The Three Seas initiative brings together 12 EU Member States - Bulgaria, Estonia, Latvia, Lithuania, Poland, the Czech Republic, Slovakia, Hungary, Slovenia, Austria, Croatia, Romania, and their partners are the United States, Germany and the European Commission. The territorial scope of the countries participating in the Three Seas covers almost one third of the European Union's territory, with 111 million European citizens living in these countries. The aim of the initiative is to promote regional cooperation and sustainable economic growth, leading to accelerated social and economic cohesion in Europe.

Bulgaria took over the coordination role in the "Three Seas" from Estonia in October 2020 at the Tallinn Summit. "During the period of its hosting, Bulgaria will develop the capacity of the initiative as a real tool for cooperation and accelerated development of our region by improving energy, transport and digital connectivity," said President Rumen Radev.