US Secretary of State Antony Blinken and Russian Foreign Minister Sergei Lavrov are to hold talks in Geneva later amid mounting fears that Russia could be about to invade Ukraine.
On Thursday Mr Blinken warned Moscow of grave consequences if any of its forces crossed the border.
Russia has 100,000 troops at the border, but denies planning to invade.
President Vladimir Putin has issued demands to the West, including that Ukraine be stopped from joining Nato.
He wants the Western defensive alliance to abandon military exercises and stop sending weapons to eastern Europe, which Moscow sees as its backyard.
Russia seized and annexed the Crimean peninsula in southern Ukraine in 2014. Ever since, Ukraine’s military has been locked in a war with Russian-backed rebels in areas near the border. The conflict has claimed 14,000 lives and caused at least two million people to flee their homes.
The summit between the top US and Russian diplomats follows moves by Mr Blinken to secure US allies’ backing for sanctions against Moscow.
After discussions in Berlin with British, French and German officials on Thursday, Mr Blinken said allowing a Russian incursion into Ukraine would “drag us all back to a much more dangerous and unstable time, when this continent, and this city, were divided in two… with the threat of all-out war hanging over everyone’s heads”.
Tensions over Ukraine
State Department officials have said that Mr Blinken will seek to offer Mr Lavrov a “diplomatic off-ramp” to ease tensions.
His comments came after US President Joe Biden on Wednesday predicted that Russia “will move in” on Ukraine and warned of a “disaster for Russia”.
But he also appeared to suggest that a “minor incursion” could attract a weaker response from the US and its allies.
The message provoked a rebuke from Ukrainian President Volodymyr Zelensky, who tweeted: “There are no minor incursions. Just as there are no minor casualties and little grief from the loss of loved ones.”
Speaking alongside Mr Blinken, Germany’s new Foreign Minister Annalena Baerbock pledged immediate action against any Russian invasion and did not rule out imposing measures that “could have economic consequences for ourselves”.
The UK’s Foreign Secretary Liz Truss has also called on Mr Putin to “desist and step back from Ukraine before he makes a massive strategic mistake” that would lead to terrible loss of life.
In a speech on Friday in Sydney, she urged Western powers to “step up” and warned that autocratic nations were being “emboldened in a way we haven’t seen since the cold war”.
Earlier this week, Britain announced it was supplying Ukraine with extra troops for training and defensive weapons.
Mr Biden is facing increasing calls from across the US political spectrum to take pre-emptive action against Russia.
Senior Republican Senator Lindsey Graham has called for “sanctions against Putin now”, while the Democratic Senator Richard Blumenthal has urged administration officials to begin “a massive airlift of … lethal weapons” to Ukrainian forces.
On Thursday the US also warned that Russian intelligence officers have been recruiting current and former Ukrainian government officials to step in as a provisional government and cooperate with an occupying Russian force in the event of an invasion.
The US Treasury Department imposed sanctions on two current Ukrainian members of parliament and two former government officials accused of being part of the plot.
“Russia has directed its intelligence services to recruit current and former Ukrainian government officials to prepare to take over the government of Ukraine and to control Ukraine’s critical infrastructure with an occupying Russian force,” a Treasury Department spokesperson said.
Your device may not support this visualisation
What do you want to know about the tensions between Russia and Ukraine? What don’t you understand that you’d like to ask one of our experts? Use the form below to submit your question.
Use this form to ask your question: