THE United States and Russia have sought to lower the temperature in a heated stand-off over Ukraine, even as they said no breakthrough was imminent in the crisis that has raised fears of a possible Russian invasion.

Armed with seemingly intractable and diametrically opposed demands, US secretary of state Antony Blinken and Russian foreign minister Sergey Lavrov met in Geneva, Switzerland, at what the American said was a “critical moment”.

With an estimated 100,000 Russian troops massed near Ukraine, many fear Moscow is preparing an invasion, although Russia denies that.

The US and its allies are scrambling to present a united front to prevent that or co-ordinate a tough response if they cannot.

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“We didn’t expect any major breakthroughs to happen today, but I believe we are now on a clearer path to understanding each other’s positions,” Blinken told reporters after the meeting.

Blinken said Lavrov repeated Russia’s insistence that it has no plans to invade Ukraine but he stressed that the US and its allies were not convinced of that.

“We’re looking at what is visible to all, and it is deeds and actions and not words that make all the difference,” he said.

Lavrov, meanwhile, called the talks “constructive and useful” and said that the US agreed to provide written responses to Russian demands on Ukraine and Nato next week. That could at least delay any imminent aggression for a few days.

But Lavrov declined to characterise that pledge.

“I can’t say whether we are on the right track or not,” he said. “We will understand that when we receive the US written response to all of our proposals.”

Moscow has demanded that the Nato alliance promise that Ukraine – a former Soviet republic – will never be allowed to join. It also wants the allies to remove troops and military equipment from parts of eastern Europe.

The US and its Nato allies have flatly rejected those demands and say that Russian President Vladimir Putin knows they are non-starters. They have said they are open to less dramatic moves.

Blinken said the US would be open to a meeting between Putin and US President Joe Biden, if it would be “useful and productive”.

Washington and its allies have repeatedly promised “severe” consequences such as tough economic sanctions – though not military action – against Russia if an invasion goes ahead.

Blinken repeated that warning yesterday before the talks.

He said the US and its allies were committed to diplomacy, but also committed “if that proves impossible, and Russia decides to pursue aggression against Ukraine, to a united, swift and severe response”.

But he said he also wanted to use the opportunity to share directly with Lavrov some “concrete ideas to address some of the concerns that you have raised, as well as the deep concerns that many of us have about Russia’s actions”.

Ukraine is already beset by conflict. Russia seized control of Ukraine’s Crimea peninsula in 2014 and backed a separatist insurgency in eastern Ukraine, part of a simmering but largely stalemated conflict with Ukrainian forces that has to date claimed more than 14,000 lives.

Putin faced limited international consequences for those moves, but the West says a new invasion would be different.