MOSCOW (AFP) - Russian Foreign Minister Sergei Lavrov on Friday warned US Secretary of State John Kerry against Washington taking "hasty" action or imposing sanctions over Ukraine, in what has escalated into the biggest East-West crisis since the Cold War.

In a telephone call, the two men followed up on their talks in Paris and Rome that had failed to lead to an agreement on how to resolve the situation in Ukraine, where Russian troops have taken effective control of Crimea.

The two diplomatic chiefs "agreed to continue looking at the problems of the sharp political crisis that has seized this country," the Russian foreign ministry said in a statement on its website.

"Lavrov warned against hasty and unthought-through steps capable of causing harm to Russian-US relations, especially sanctions that will inevitably have a boomerang effect against the US itself," it added.

The US State Department confirmed that Mr Kerry had spoken with Mr Lavrov Friday from his plane.

US President Barack Obama previously talked by phone with Russian President Vladimir Putin for an hour about Ukraine, including a visa ban and possible further sanctions against Russian officials, the White House said.

The United States is suggesting that international mediation efforts could bring Ukraine and Russia together for discussions.

State Department spokesman Jen Psaki said that Washington was discussing with its partners the formation of some kind of contact group, even though Moscow is likely to be distrustful of outside engagement.

"The issue here is getting Russia and the new government in Ukraine at the same table having a discussion, and there are a range of partners and players in the international community that can be a part of that," she told reporters.

"Russia is fairly isolated here from where the international community is," Ms Psaki said, adding many countries had denounced its moves in Crimea as "illegal and inappropriate." But she said: "There are still partners who would be willing to and happy to be a part of bringing an end to this through diplomatic channels."