Putin reportedly requested a telephone call between the two leaders for Monday 14 February, but a White House official said that Biden wanted to conduct talks earlier.
On Friday, the US warned of the “very distinct possibility” of a Russian invasion into Ukraine in the coming days, and instructed all Americans to leave the country within the next 48 hours.
Citizens urged to leave Ukraine
A number of other countries have also asked their citizens to leave Ukraine, including Australia, New Zealand, Japan, Latvia, Norway and the UK.
The Foreign Office updated its advice on Friday evening to urge UK nationals to “leave now while commercial means are still available”.
Britons are being urged to flee Ukraine immediately because Russia has amassed the firepower to attack “at no notice”, as diplomatic efforts to avert war continue.
Nato allies were ordering citizens to leave while fears grew that Putin could order an invasion in the coming days.
Russia could attack ‘very quickly’
Armed forces minister James Heappey said with the Kremlin having amassed weaponry and an estimated 130,000 troops on Ukraine’s border, Russia could attack “very, very quickly”.
Unlike when the Taliban seized Kabul, Heappey stressed that the RAF would not be carrying out evacuations in the event of war in Ukraine, which is not a Nato member.
“We are now confident that the artillery systems, the missile systems and the combat air are all in place that would allow Russia to launch – at no notice – an attack on Ukraine,” he told BBC Breakfast.
“And on that basis I think it is our responsibility to share with UK citizens our view that they should leave the country immediately while commercial means are still available.
“There will be a big difference between what they may have seen on their TV screens in Afghanistan over the summer and what may happen over the next week or so and that is that the Royal Air Force will not be in a position to go in and to fly people out so they need to leave now by commercial means or drive out of Ukraine into a neighbouring country.”
British ambassador to Ukraine Melinda Simmons was remaining with a “core team” in Kyiv, but some embassy staff and their families were being withdrawn.
Heappey said it was necessary to maintain a diplomatic presence while a possibility of talking down tensions remains.
“That’s a brave thing for our diplomats to want to do, given that there will effectively be no notice now, if Putin decides to go, everything is in place for him to be launching strikes on Ukraine within minutes,” he told Times Radio.
“Because diplomacy needs to be given a chance it is an infinitely better outcome than what could be just the most catastrophic waste of life in the biggest war that we’ve seen in Europe since 1945.”
Invasion could come ‘at any time’
It is understood that the Foreign Office’s order was issued as intelligence and advice from experts on the ground suggested an increased threat level, with an invasion at some point deemed highly likely.
Biden and Putin will discuss the crisis by phone on Saturday, as the Pentagon orders an extra 3,000 troops to Poland to support allies.
Defence Secretary Ben Wallace said an invasion could come “at any time”, while US national security adviser Jake Sullivan said an attack before the end of the Winter Olympics on February 20 is a “credible prospect”.
Western leaders have threatened Moscow with a damaging package of sanctions in the event of a further incursion into Ukrainian soil.
Heappey rejected a call from Ukrainian ambassador Vadym Prystaiko for Britain to send combat troops to Ukraine to deter an attack.
“Putin and his colleagues would very much like to be able to say is what they may do is a consequence of Western aggression in Ukraine,” he told BBC Breakfast.
“So it’s very important to us, to everybody frankly involved, that we’re very clear we won’t play an active part in Ukraine.”
The UK personnel sent to train Ukrainians to use British-supplied anti-tank missiles will be “leaving over the course of the weekend”, Heappey told BBC Radio 4’s Today programme.
Polish prime minister Mateusz Morawiecki, who met Boris Johnson in Warsaw this week, urged Europe to go further in applying financial pressure on Moscow.
“Faced with a growing Russian threat, European governments have largely reacted passively. Leaders have lacked the courage or determination to cut business ties with the Kremlin,” he wrote in the Daily Telegraph.
“The noose is tightening around Europe’s neck, not Moscow’s.”
British troops to be withdrawn
Heappey said British troops helping with training in Ukraine will be leaving the country this weekend.
Having sent UK personnel to train Ukrainians on the anti-tank missiles supplied by Britain, Heappey said: “All of them will be withdrawn. There will be no British troops in Ukraine if there is to be a conflict there.”
He added to BBC Radio 4’s Today programme: “They will be leaving over the course of the weekend.”
Additional reporting by PA
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