Russian Foreign Minister Sergei Lavrov and U.S. Secretary of State John Kerry discussed proposals for resolving the crisis in Ukraine during a telephone conversation on Thursday, the Russian Foreign Ministry said.
Lavrov and Kerry are due to meet in London on Friday.
Barack Obama warned Russia that the West will be forced to apply a cost to Moscow if it fails to change course in its dispute with Ukraine.
The ballot paper that the people of Crimea will use in Sunday's referendum was published today
Vitali Klitschko's visit to the eastern city of Donetsk is clearly an attempt to try to ease the divisions with Ukraine.