Poland on Thursday signed a landmark deal to build the first EU gas pipeline to the isolated Baltic countries and lessen their reliance on Russia.

"You have witnessesed history being made," European Commission President Jean-Claude Juncker said after witnessing the signing of the 558-million-euro ($636 million) deal by energy representatives from Poland, Lithuania, Latvia and Estonia.

"You have ended the energy isolation of the Baltics. You have ended their long-lasting dependence on a single supplier," Juncker said.