While trilateral gas talks between the European Union, Russia and Ukraine continue, gas supplies should not stop, European Commission President Manuel Barroso said in his letter on behalf of the EU in response to Russian President Vladimir Putin.

"I count on the Russian Federation to maintain this commitment. It therefore continues to be Gazprom's responsibility to ensure the deliveries of the required volumes as agreed in the supply contracts with European companies," Barroso said in his letter, which was released by the European Commission in Brussels.

Russia is also expected to activate the early warning system well in advance if such a need arises, the document said.