At last year's summit of the Three Seas Initiative in Bucharest, Perry first announced the launch of the Partnership for Transatlantic Energy Cooperation, a move seen as an effort to steer Europe away from Russian gas.

In his address in Bucharest, Perry talked about cutting dependence on Russia and the importance of diversifying energy sources, according to a statement released by the US Energy Department after the meeting.

Today's ministerial features representatives of the European Commission and the relevant ministers of all 27 EU member states.

Recently, Slovenian President Borut Pahor suggested that a high representative of the US, "maybe even the highest", would come to Slovenia for the Three Seas Initiative summit this year.

In her meeting with Perry, Bratušek underlined the importance of cooperation between the EU and the US to ensure energy security, diversification of resources and faster introduction of renewables, according to a press release from the Slovenian embassy in Washington.

Perry underlined the importance of energy security for national security and expressed the expectation that the ministerial would serve as a foundation upon which to address the challenges.