The 3SI began to meet and talk to each other as a forum for leaders and civil servants: the “three seas” on its behalf refer to the Adriatic, the Baltic Sea and the Black Sea, the waters on which the Member States have a coastline. The third summit of the initiative was held in Bucharest from 17 to 18 September 2018. Participants approved a list of priority interconnection projects in the three key areas of transportation, energy and digital.  European Commission President Jean-Claude Juncker, German Foreign Minister Heiko Maas and US Energy Secretary Rick Perry attended the summit. The first edition of the Economic Forum was organized at that time. 3SI Network of Chambers of Commerce was created and Letter of Intent as part of the creation of the Three Seas Investment Fund was signed here.   At the 3SI Bucharest Summit in 2018, a list of 48 priority interconnection projects was agreed on the three pillars of energy, transport and digital. The EU is expected to fund about half of these projects, with the EU`s largest funds to date being spent on multilateral energy and transport projects. The Fund`s first projects are expected to be announced before the end of the year. U.S. Ambassador to Poland Georgette Mosbacher commented on the agreement to strengthen the strategic partnership between the two countries, as did the U.S. Ambassador to Poland: in 2018, the summit was held in Bucharest, Romania, and included the first economic forum of the three seas.
At the Economic Forum, an agreement was reached on 3SI`s priority interconnection projects, which includes a total of 48 projects in two categories (multilateral and bilateral and national projects with international potential) in three sub-categories (digital, energy and transport). In accordance with the agreement, the two sides will prepare, within 18 months, a report on the results of the preparatory work of major U.S. companies in the civil nuclear sector and a proposal on the funding structure of the programs. The absolute loser of the three pillars of 3SI, energy, transport and technology, seems to be Russia, which will simply be less relevant to the central European economies. “This agreement marks several important milestones; Not only is this strengthening Polish-American relations, but it is also an announcement to the rest of the world that America is back in nuclear power thanks to advanced American technology. In the area of transport infrastructure, Hungary is already pursuing With Chinese funding to improve its rail link with Serbia, with the Belgrade to Budapest railway being a BIS project at a higher speed, although it largely relies on opaque decision-making in the region. 3SI could, over time, extend a high-speed line to Warsaw? Bulgaria has reached a framework agreement with China for the construction of four motorways and a tunnel. It is not yet known how such projects with Chinese participation can be integrated into the 3SI or whether they are maintained separately, which seems more likely. The current initiative is influenced by the Polish concept of intermarium between the two wars. The modern three-sea initiative was launched in 2015 by Polish President Andrzej Duda and Croatian President Kolinda Grabar-Kitarovic.
 Its first summit was held on 25 and 26 August 2016 in Dubrovnik, Croatia. The two-day event ended with a declaration of cooperation on economic issues, particularly in the area of energy infrastructure and transport and communication.  Polish President Andrzej Duda called the initiative “a new approach to promoting the unity and cohesion of Europe, it is an idea of cooperation between 12 countries between the Adriatic, the Baltic Sea and the Black Sea, the three seas of Central Europe”. Among the guest speakers were Liu Haixing, Chinese Foreign Affairs Assistant, who spoke about the Chinese government`s commitment to the Belt and Road initiative, and the former U.S. National Security Adviser, General James L.