Three Seas Initiative: Members, Infrastructure and Geopolitics

The Three Seas Initiative is a cooperation forum for European countries located between the Baltic Sea, the Adriatic Sea and the Black Sea. It brings together 13 European Union member states to expand transport, energy and digital infrastructure connections along the continent’s north-south axis. The format does not operate as a classic international organization: it has no founding treaty, strong secretariat or budget comparable to the EU’s. Its weight comes from a political coordination mechanism that turns national bottlenecks into a regional agenda. First, presidential summits define common priorities. Business forums then present those priorities to banks, companies and investors. Only after that do project lists give political visibility to works that, on their own, would look merely national.

The gap that organizes the initiative is easy to understand but politically deep. After the Cold War, many of these countries became better connected to Germany, Austria and other Western economies. North-south links inside the region itself, however, remained weaker. For this reason, a transport or energy project stops being only public infrastructure when it changes the routes available to several countries. Each new connection expands a government’s options during crises by reducing dependence on a single route or dominant supplier.

Summary

• The Three Seas Initiative tries to reduce transport, energy and digital infrastructure bottlenecks that leave Europe’s north-south axis less integrated than routes oriented toward the west.
• Its participating core consists of 13 EU member states, which keeps the forum inside the single market and requires it to work with European rules, funds and priorities.
• The four associated states, Ukraine, Moldova, Albania and Montenegro, take part as reconstruction, EU enlargement, route security and shared infrastructure have become connected agendas.
• The initiative presents itself as complementary to the EU while giving Central and Eastern European countries their own platform for defending connectivity, energy security and military mobility.
• Priority projects illustrate different functions of infrastructure. Via Carpatia, Rail Baltica and Rail2Sea reorganize transport corridors. BRUA, the Krk LNG terminal and Baltic electricity synchronization expand energy and strategic options.

Origin and Meaning of the Name

The name “Three Seas” refers to the European space between the Baltic, Adriatic and Black seas. The expression designates a group of states that occupy the central and eastern belt of the European Union, from the Baltic north to southeastern Europe. The initiative was launched politically by Polish and Croatian leaders in the mid-2010s, and its first presidential summit took place in Dubrovnik in 2016.

The starting point was economic, although the economy was never separated from geopolitics. After the Cold War and the EU’s eastward enlargement, many countries in the region entered the single market. They received European funds and became better connected to Germany, Austria and other Western economies. Yet the connection between the Baltic, Adriatic and Black seas remained uneven. In practice, moving between the north and south of the region could still be harder than moving west.

That pattern had historical roots. During the Soviet and socialist period, part of Central and Eastern Europe’s infrastructure served production chains, military routes and energy dependencies oriented toward the east. Integration with the EU after 1989 corrected part of that legacy. Even so, the asymmetries persisted. The Three Seas Initiative emerged to turn that regional perception into a political program. Without denser north-south links, the countries between the three seas would remain more dependent on third parties for energy, investment, port access and joint crisis response.

Members, Associated States and Strategic Partners

The core of the initiative consists of 13 European Union member states, which places the forum inside the European single market. This institutional base distinguishes it from an alliance outside the EU:

• Austria;
• Bulgaria;
• Croatia;
• Czechia;
• Estonia;
• Greece;
• Hungary;
• Latvia;
• Lithuania;
• Poland;
• Romania;
• Slovakia;
• Slovenia.

The 12 original participants were countries of Central Europe, the Baltic region and southeastern Europe that were already integrated into the EU. Greece’s entry expanded the forum’s southern reach and brought the Three Seas agenda closer to the Aegean and the eastern Mediterranean. As a result, Greek ports, Balkan railways and southeastern European energy routes gained greater weight in the discussion of corridors between the north and south of the continent.

The initiative created a category for countries outside the core of EU members. Ukraine and Moldova received the status of associated participating states after Russia’s invasion of Ukraine and the advance of their processes of rapprochement with the European Union. In 2025, Albania and Montenegro were welcomed into the same category. This enlargement does not replace formal EU accession negotiations. Its function is to open a political table where infrastructure, reconstruction, route security and economic integration can be discussed before or alongside the European enlargement process.

Strategic partners enter this arrangement given the region’s dependence on rules, capital and technology that the members do not control on their own. The European Commission keeps the initiative connected to the EU’s financial and legal instruments. Germany follows the forum as Central and Eastern connectivity affects production chains, energy and commercial circulation linked to the bloc’s largest economy. The United States has supported the format from early on for energy and strategic reasons, especially to reduce regional dependence on Russian gas and expand its own economic presence. Japan, Spain and Turkey widen that circle by offering external channels of investment, technology and economic diplomacy, although their roles vary by summit and project.

Institutional Structure

The Three Seas Initiative operates more as a political platform than as a bureaucracy. Its summits bring together presidents, heads of government or high-level representatives. Alongside them, the Three Seas Business Forum connects governments with development banks and infrastructure investors. This arrangement helps turn political priorities into financeable projects, although it does not by itself guarantee that the works will be built.

The group works with priority projects, progress reports and financial instruments. The initial list of interconnections was presented at the 2018 Bucharest summit, with 48 initiatives. By the mid-2020s, official reports already recorded more than one hundred projects, with an estimated value above 100 billion euros. That growth shows that the forum has gained reach. At the same time, it reveals the difference between political priority and material execution. The same list can include a completed work, a corridor under construction and a project that still depends on studies, permits and investors.

The Three Seas Initiative Investment Fund was created to bring private capital and public development banks closer to the agenda. Its commercial design distinguishes it from a European cohesion fund. Instead of distributing budgetary grants, it seeks to invest in assets that can generate returns and expand regional connectivity. That logic includes energy, transport and digital infrastructure. In 2025, the Warsaw declaration recorded the preparation of later instruments, including an innovation fund with initial participation by Poland, Czechia, Hungary and Croatia. These mechanisms still depend on EU resources, national budgets and private financing. Their function is to give the initiative a more operational dimension than that of an ordinary diplomatic conference.

The North-South Gap

The problem that organizes the initiative is the difference between east-west and north-south connections. For decades, many of the region’s commercial and energy routes were oriented toward centers of power outside the three-seas belt itself. These countries’ entry into the EU gave political and economic priority to links with Western Europe. By contrast, connections among the Central and Eastern European countries themselves remained fragmented, creating bottlenecks precisely where regional integration depended on physical continuity across borders.

This fragmentation creates practical costs. A cargo shipment leaving a Baltic port for the Balkans, for example, may face incompatible railway sections. The lack of intermodal terminals or complete road corridors increases travel time and reduces commercial predictability. For a landlocked country, access to ports depends on stable agreements with neighbors and on customs services that work without political blockage. In the energy sector, the same logic applies to electrical grids and gas: an LNG terminal gains regional value only when pipelines can carry the fuel to other countries.

In this way, infrastructure stops being merely a set of national works. It becomes a condition that allows small and medium-sized states to negotiate with more options. When a state in the region invests in ports or energy networks, the gain can reach neighbors that depend on those connections. The initiative tries to give regional form to that effect by coordinating projects that, in isolation, would be treated as domestic works.

Transport: Routes, Ports and Military Mobility

Transport projects are the most visible component of the Three Seas Initiative. Via Carpatia is a planned road route intended to link the Baltic to southeastern Europe. Its route brings Lithuania closer to Greece through a sequence of countries across the center-east of the continent. The function of the road goes beyond shortening journeys. By creating a north-south artery, it can connect peripheral regions, bring ports closer together and reduce dependence on routes concentrated along the western axis.

Rail Baltica plays a similar role in the north. The project seeks to integrate Estonia, Latvia and Lithuania into a railway network compatible with broader European standards, facilitating the link between the Baltic states, Poland and the rest of the EU. For the Baltic countries, the railway has commercial value and reduces a strategic vulnerability: dependence on infrastructure inherited from a post-Soviet logic and less connected to the European rail space.

Another example is Rail2Sea, designed to connect the Polish port of Gdańsk on the Baltic to the Romanian port of Constanța on the Black Sea. A route of this kind connects trade, military logistics and maritime access. In ordinary times, it can facilitate the movement of goods. In a security crisis, it can help move equipment, supplies and forces between the northern and southeastern parts of NATO’s eastern flank.

For that reason, the 2025 Warsaw declaration highlighted military mobility. The expression refers to the ability to transport troops and heavy equipment without delays incompatible with a crisis. Roads, bridges and railways must be able to support that use without paralyzing civilian circulation. The war against Ukraine made the issue less abstract. Civilian infrastructure that serves commerce can support territorial defense, evacuation and allied supply.

Energy: Diversification and Interdependence

The initiative’s energy agenda was born from an old vulnerability: the dependence of part of Central and Eastern Europe on resources or networks influenced by Russia. That dependence varied from country to country, but it produced a common political effect. When one supplier dominates routes, prices and contracts, it gains room to pressure governments during disputes.

LNG terminals change part of that equation by allowing gas imports by ship. The Polish terminal at Świnoujście on the Baltic and the Croatian terminal on the island of Krk in the Adriatic expand regional options when they are connected by pipelines and interconnectors. The value of LNG lies not only in the fuel received at the port, but in the ability to redistribute energy through a more flexible network, reducing a single supplier’s capacity to condition the foreign policy of neighboring countries.

The BRUA corridor, associated with Bulgaria, Romania, Hungary and Austria, illustrates the same logic. A regional pipeline or interconnection changes geopolitics only when it permits reverse flow, access to different sources and bargaining among several markets. Otherwise, the work merely shifts dependence from one route to another. The Three Seas Initiative tries to avoid that outcome by treating energy as a regional system, not as an isolated bilateral contract.

Baltic electricity shows another mechanism. For years, Estonia, Latvia and Lithuania maintained technical ties with networks inherited from the post-Soviet space. Synchronization with continental European grids reduced that exposure and brought the three countries closer to the EU electricity market. In this case, infrastructure defines the technical system that regulates frequency, stability and response to failures.

Digital Infrastructure and “Smart Connectivity”

The initiative’s digital dimension extends the agenda beyond roads, rails and pipelines. Fiber-optic networks and data centers can increase the efficiency of physical infrastructure. The same is true of 5G, high-performance computing and cybersecurity. A railway with digital control, a port with integrated documentation and an electrical grid capable of handling distributed renewable generation produce different gains from a work built only from concrete and steel.

The idea of “smart connectivity” emerged to name this integration between physical infrastructure and digital services. It starts from the premise that energy, transport and data now operate together. A freight route depends on customs systems, tracking, document interoperability and logistics platforms. An electrical grid with renewable energy requires measurement, storage, demand forecasting and rapid information exchange among operators. A regional market works well only when countries can share technical standards and reliable data.

This agenda has a geopolitical dimension: digital infrastructure depends on suppliers, security standards and data-protection rules. By bringing the topic into the Three Seas Initiative, the countries in the group try to prevent regional connectivity from being built only through dispersed commercial decisions. The concern is that critical networks, if poorly regulated or excessively dependent on external suppliers, may create new vulnerabilities instead of reducing old ones.

Relationship with the European Union

The Three Seas Initiative presents itself as complementary to the European Union. That formula responds to a real tension. For its defenders, the forum helps Central and Eastern European countries identify bottlenecks that the EU’s general mechanisms address slowly or in dispersed ways. For its critics, the initiative could reinforce a division between “old” and “new” Europe, especially if it were used as a political bloc against Brussels, Berlin or Paris.

In practice, the initiative depends on the EU at several levels. Many projects must respect European rules on competition, procurement and the environment. Financing intersects with cohesion funds and trans-European network policies. Without this institutional fit, the initiative would struggle to turn political declarations into works accepted by the single market.

At the same time, the platform gives regional voice to countries that cannot always impose priorities in the broader EU debate. This function appears in projects of different kinds. A road on the border between Poland and Slovakia reinforces regional road continuity. The modernization of a Baltic railway reduces logistical isolation. The expansion of a Croatian terminal widens energy alternatives. In the Three Seas framework, these works appear as parts of a network that strengthens cohesion, energy security and mobility on the bloc’s eastern flank.

The United States, Germany and the Transatlantic Dimension

United States support for the Three Seas Initiative follows from the way the forum connects infrastructure, energy and strategy. The U.S. presence at the 2017 Warsaw summit gave the forum international visibility and brought the energy-security agenda closer to transatlantic politics. For Washington, LNG terminals, interconnectors and north-south routes reduce Russia’s ability to use energy as an instrument of pressure. These works create space for U.S. companies, technology and financing as well.

Even with that convergence, the initiative remains anchored in regional interests of its own. Some members balance their relationship with the United States, Germany, the European Commission and neighbors with different political positions. Hungary, for example, has maintained a more ambiguous posture toward Russia over the years than Poland or the Baltic states. These differences limit the forum’s capacity to act as a uniform geopolitical bloc.

Germany occupies a sensitive position. As the EU’s largest economy, Berlin influences infrastructure, energy and the European budget. Without some form of German involvement, the initiative would be disconnected from a central part of the European market. At the same time, some Three Seas countries viewed projects such as Nord Stream with suspicion: the pipeline carried Russian gas directly to Germany through the Baltic Sea and bypassed transit countries in Central and Eastern Europe. German participation as a strategic partner helps reduce the interpretation that the initiative is an anti-Berlin grouping. Disputes over energy and industrial priorities, however, remain present.

Ukraine, Moldova and European Enlargement

Russia’s invasion of Ukraine changed the political function of the Three Seas Initiative. Before 2022, the forum already addressed energy security and regional connectivity. With the war, those areas became directly linked to Ukraine’s economic survival. The movement of exports, the displacement of refugees and future reconstruction entered the same agenda as Kyiv’s and Chișinău’s rapprochement with the European Union.

Ukraine needs routes that connect it to the European market even when the Black Sea is vulnerable to blockades, attacks or maritime insecurity. Railways, roads, dry ports, energy networks and digital connections can serve that function. Moldova, in turn, faces limits of scale, energy dependence and geopolitical pressure linked to the Russian presence in Transnistria. By bringing these countries closer to the Three Seas agenda, the forum creates a space where reconstruction, European integration and regional security are discussed together.

This rapprochement has limits. The status of associated participating state does not provide NATO guarantees, does not amount to EU entry and does not resolve territorial disputes. Even so, it helps fit Ukraine and Moldova into connectivity projects that can prepare deeper economic integration. In the Western Balkans, the association of Albania and Montenegro follows a similar logic: infrastructure can anticipate part of practical integration before the political process of EU accession is completed.

Criticism and Limits

The main limitation of the Three Seas Initiative is the distance between ambition and execution. A list with many projects does not mean that all of them have financing, permits, local support, technical maturity or economic viability. Some projects advance when they already fit national or European priorities. Others remain political signals while they wait for studies, investors or consensus among governments.

Another limit is the political heterogeneity of the members. Poland and the Baltic states tend to interpret the initiative through the lens of security vis-à-vis Russia. Austria has different interests, because it is landlocked and economically connected to Central Europe. Greece brings the eastern Mediterranean and the Balkans into the equation. Hungary often adopts its own positions on energy, Russia and European politics. These differences keep cooperation concentrated on infrastructure and reduce the likelihood that the forum will act as a common strategy on more sensitive issues.

A further criticism concerns institutional duplication. Since the EU already has cohesion policies, trans-European networks, energy programs and financing instruments, some observers ask whether the initiative creates its own value or merely repackages existing projects. The answer depends on the case. When the forum gives political visibility, brings investors closer and coordinates cross-border sections, it can accelerate priorities that would otherwise remain dispersed. When it only incorporates works already planned through other channels, its role is closer to that of a diplomatic showcase.

What the Initiative Changes in European Politics

The Three Seas Initiative turns infrastructure into a common diplomatic language for countries with different histories and strategic positions. A port on the Adriatic or a Baltic railway does not resolve European divisions on its own. The same is true of a Romanian pipeline, a Hungarian data center or a road in the Carpathians. Yet when these projects reduce bottlenecks across borders, they expand options for trade, energy, defense and integration.

The forum reflects a shift in European politics after 2022. Security is not limited to tanks, troops and military treaties. It depends on the industrial capacity that produces equipment, the ports and bridges that move it, the electrical grids that keep societies functioning and the digital systems that connect administration, semiconductors and artificial intelligence to civilian and military logistics. The war in Ukraine made visible that civilian infrastructure can support resistance, supply and reconstruction, while its absence can turn borders into chokepoints.

The initiative’s reach should therefore be measured less by its ability to act as a political bloc and more by its ability to connect projects that change the choices available to states in the region. If it manages to finance and complete north-south corridors, energy interconnectors and secure digital networks, the Three Seas Initiative will reduce vulnerabilities that geography and history left in Central and Eastern Europe. If it remains concentrated on declarations and extensive lists without execution, it will continue to function as a useful signaling forum and will have limited effect on the real distribution of power and infrastructure in Europe.