Biden told this at an Atlantic Council meeting in Istanbul, Censor.NET reports, referring to Deutsche Welle.
"Now is the time to act. The situation in Ukraine only underscores the urgency of the matter. Europe needs to ensure it diversifies", Biden said.
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He also suggested that the crisis in Ukraine had again showed up "Russia's track record in using energy supplies as a form of a political weapon against neighbours. "It's a huge strategic problem", he told the conference.
"Russia "will and should remain" a major supplier of energy to Europe... Russia can be a player but must play by the rules of the game. It cannot play with the game", Biden stressed.