US Secretary of State John Kerry has met with Russia's Foreign Minister Sergei Lavrov in Paris for hastily organised talks after the Kremlin set out demands for a diplomatic resolution to the Ukraine crisis.
Sunday's talks came after Russian President Vladimir Putin called his US counterpart Barack Obama on Friday to say he was interested in discussing a US proposal on the table to resolve the standoff over Ukraine.
Appearing on Russian television ahead of his talks with Kerry, Lavrov rejected suspicions that the deployment of tens of thousands of Russian troops near Ukraine was a sign Moscow was planning to invade the country following its annexation of the Crimean peninsula.
"We have absolutely no intention of, or interest in, crossing Ukraine's borders," Lavrov said.
Russia says the troops near the border are there for military exercises and that they have no plans to invade, but US and European officials say the numbers and locations of the troops suggest something more than exercises.
US, European and Ukrainian officials are deeply concerned about the build-up, which they fear could be a prelude to an invasion or intimidation to compel Kiev to accept Moscow's demands.
In his interview, Lavrov made clear that Moscow believes a federation is the only way to guarantee Ukraine's stability and neutrality.
"We can't see any other way to ensure the stable development of Ukraine but to sign a federal agreement," Lavrov said, adding that he understood the US was open to the idea.
US officials have been coy about their position on a federation and insist that any changes to Ukraine's governing structure must be acceptable to the Ukrainians.
Ukrainian officials are wary of decentralising power, fearing that pro-Russia regions would hamper its western aspirations and potentially split the country.
However, they are exploring political reforms that could grant more authority to local governments.