The Three Seas Initiative (TSI, 3SI)
also known as the Three Seas, is the term describing a project of political and economic cooperation, especially in the fields of infrastructure, transport and energy. The TSI was launched in 2016 and links the European Union countries located in the area traditionally referred to as the Intermarium: Austria, Bulgaria, Croatia, Czech Republic, Estonia, Lithuania, Latvia, Poland, Romania, Slovakia, Slovenia and Hungary. The main aim of the TSI is to develop cooperation between its member countries within the European Union and to strengthen ties with the USA, above all in the field of energy cooperation. The forms of cooperation between TSI member countries have not been institutionalised and political coordination has so far been carried out mainly at the presidential level of the member states. Furthermore, the Three Seas is not an international organisation and is still in its initial stage of formation.
The official website of the Three Seas Initiative

“Państwa Inicjatywy Trójmorza”/”Three Sea Initiative States”