U.S. vows more sanctions on Russia unless tensions ease in Ukraine

WASHINGTON (Reuters) - U.S. Secretary of State John Kerry told Russian Foreign Minister Sergei Lavrov in a telephone call on Tuesday that Washington would impose more sanctions on Russia if tensions did not de-escalate in eastern Ukraine, a senior U.S. official said.

The official said Kerry talked to both Lavrov and Ukrainian Prime Minister Arseny Yatseniuk.