ABOARD AIR FORCE ONE (AP) -
The White House says President Barack Obama has spoken to German Chancellor Angela Merkel about the situation in Ukraine.
White House spokesman Jay Carney says Obama spoke to Merkel from Air Force One as he flew back to Washington on Thursday. He characterized the call as a "check-in" between the leaders.
The call comes amid increasing concern in Europe that the Ukraine crisis could lead to a cut-off of Russian gas. Russian President Vladimir Putin has told European leaders that Ukraine's growing debts to Moscow can threaten supplies to Europe. A large portion of Europe's gas comes from Russia through Ukraine.
Germany is a key U.S. ally in NATO. Merkel has spoken to Putin during the conflict.
The White House says further details about the call will be released later.