The US is warning of more sanctions against Russia, if tensions continue in eastern Ukraine. US Secretary of State John Kerry talked to both Russian Foreign Minister Sergei Lavrov and Ukrainian interim Prime Minister Arseny Yatseniuk on Tuesday.

Kerry has urged Russia to tone down its rhetoric and engage diplomatically with the Ukrainian interim government. But Lavrov says Ukraine has not been serious in implementing an agreement reached in Geneva last week, which was aimed at defusing the crisis.