At the seventh summit in Riga on 20 June 2022, Ukraine received the status of a partner-participant of the TSI, de facto becoming a participant in this initiative.

[6] The Initiative's first summit, held in Dubrovnik, Croatia, on 25–26 August 2016, ended with a declaration of economic cooperation in energy and in transport and communications infrastructures.

[14] Guest attendees included President of the European Commission Jean-Claude Juncker, German Foreign Minister Heiko Maas, and US Secretary of Energy Rick Perry.

A 3SI Network of Chambers of Commerce was created, and a letter of intent was signed concerning establishment of a Three Seas Investment Fund.

[33][34] The initial two founding institutions from Poland and Romania have committed themselves to make payments totaling more than 500 million euros.

The supervisory board of the Fund consists of representatives of development banks from Poland, Romania, Latvia, and the Czech Republic.

[39] The fund is to focus on projects creating transport, energy and digital infrastructure in the Three Seas region.

Some of those objections have been partially addressed lately also due to a good experience with cooperation on infrastructure projects in the Visegrád Group.

"[52] In October 2019, Polish Foreign Minister Jacek Czaputowicz said that Ukraine could not now join the Three Seas Initiative, as it includes the countries of Central and Southern Europe, which are members of the European Union.

Speaking about cooperation in the energy sector, Zelenskyy reminded that Ukraine has one of the largest gas storage facilities in the region.

[57] At this summit Ukraine received the status of a partner-participant of the TSI, de facto becoming a participant in this initiative.