Russia and the United States gave no sign that they had narrowed their differences on Ukraine and wider European security in talks in Geneva on Monday, as Moscow repeated demands that Washington says it cannot accept, Reuters reports. 

Russia has massed troops near Ukraine's border while demanding that the U.S.-led NATO alliance rule out admitting the former Soviet state or expanding further into what Moscow sees as its back yard.

"Unfortunately we have a great disparity in our principled approaches to this. The U.S. and Russia in some ways have opposite views on what needs to be done," Russian Deputy Foreign Minister Sergei Ryabkov told reporters.

Deputy U.S. Secretary of State Wendy Sherman said: "We were firm ... in pushing back on security proposals that are simply non-starters to the United States."

Washington and Kyiv say 100,000 Russian troops moved to within striking distance of Ukraine could be preparing a new invasion, eight years after Russia seized the Crimean peninsula from its neighbour.

Russia denies any such plans and says it is responding to what it calls aggressive behaviour from NATO and Ukraine, which has tilted toward the West and aspires to join the alliance.

Ryabkov repeated a set of sweeping demands including a ban on further NATO expansion and an end to the alliance's activity in the central and eastern European countries that joined it after 1997.

"We underscore that for us it’s absolutely mandatory to make sure that Ukraine never, never, ever becomes a member of NATO," he said.

"We do not trust the other side, so to say. We need iron-clad, waterproof, bulletproof, legally binding guarantees. Not assurances, not safeguards, guarantees with all the words 'shall, must', everything that should be put in, 'never ever becoming a member of NATO'. It’s a matter of Russia’s national security."

Sherman said: "We will not allow anyone to slam closed NATO's open-door policy, which has always been central to the NATO alliance.

"We will not forego bilateral cooperation with sovereign states that wish to work with the United States, and we will not make decisions about Ukraine without Ukraine, about Europe without Europe, or about NATO without NATO."