Russia must pull back troops from Ukraine border: Kerry

US Secretary of State John Kerry has told his Russian counterpart Sergei Lavrov that Russia must pull back its troops from the Ukrainian border to deescalate the tension following Crimea's takeover by Moscow.

"Any real progress in Ukraine must include a pullback of the very large Russian force that is currently massing along Ukraine’s borders," Kerry said at a news conference in Paris on Sunday after four hours of talks with Lavrov.

"We believe that these forces are creating a climate of fear and intimidation in Ukraine. It certainly does not create the climate that we need for the dialogue and for the messages sent to both the international community as well as to Ukrainians themselves about the diplomatic channel," he said.

Kerry said he and Lavrov made suggestions on how they can deescalate the security as well as the political situation in and around Ukraine.

"We talked very seriously and at length about the impact of the massing of troops and the importance of including the drawdown and redeployment of some of those troops with respect to the process moving forward," he said.

It's not up to the US or Russia to make any decision or any agreement regarding federalization, Kerry said.

Kerry also ruled out discussion of Russia's demand for Ukraine to become a loose federation until-and-unless Ukrainians are at the table.

"We talked about it. But it's up to Ukrainians, and Ukrainians will decide their future for themselves, by themselves, with respect to what kind of definitions work for them. And it will have to be an input, obviously, of what the Russian view is," he said.

"And so tonight we did not explore that because it would have been inappropriate for me to do so without Ukrainian input directly with respect to that."

"What we are looking for is how do we deescalate it, how do we get on a track to be able to give the Ukrainians the opportunity that they deserve to be able to do that," Kerry said.

Kerry said the Ukrainian government has demonstrated remarkable restraint in the face of enormous pressure.

"It has shown the world a kind of courage and resilience that every country ought to applaud. And as it continues down this path, the United States of America and our partners will remain firmly by its side," he said.