The Three Seas Initiative is an infrastructure and energy cooperation project involving 12 Central and Eastern European countries stretching from the Baltic to the Adriatic and Black seas.
Duda said that the project, which was initiated in 2015, is now blooming, with even the US, German, French and Japanese leaders taking part in a Three Seas Summit in Bulgaria this week.
"This shows that our partners, who have huge global economies, can see the great potential in our cooperation," Duda said in Sofia on Friday. "There are 120 million EU citizens in the Three Seas region and the Three Seas is now a huge part of Europe's economic growth, and the fastest-growing part of Europe."
Quoting World Bank and International Monetary Fund data, the Polish president said that the region could see growth figures of up to 4.8 percent this year.
Duda also dismissed critics who have warned that the regional initiative could weaken the EU
"For me, cooperation within the Three Seas is an important element in the development of the European Union," he said.
The Three Seas Initiative was established by the Polish and Croatian presidents to promote cross-country energy and infrastructure links. (PAP)