Russian Foreign Minister Sergei Lavrov and US Secretary of State John Kerry have arrived in Paris for crisis talks on Ukraine.
The meeting was hastily arranged after President Vladimir Putin phoned President Barack Obama on Friday.
Russia has annexed Crimea and there are reports of thousands of Russian troops massed close to Ukraine’s borders.
Earlier Lavrov set out demands for a neutral and federal Ukraine, an idea Kiev called “full capitulation”.
However, Lavrov has categorically denied any plans for an invasion.
But he has stressed Moscow will protect the rights of ethnic Russians and Russian speakers, after pro-EU protests in Kiev led to the ousting of Ukraine’s President Viktor Yanukovych. He had faced months of protests after pulling out of an association deal with Brussels.
On Sunday the US ordered its top general in Europe to return early from a trip to Washington.
Gen Philip Breedlove, Nato’s supreme allied commander Europe, had been due to testify to Congress, but a Pentagon spokesman told Reuters his return was prudent “given the lack of transparency and intent from Russian leadership about their military movements across the border”.