Biden and Putin to speak by phone: Last-ditch talks on Russian threat to invade Ukraine

• Joe Biden will speak to Vladimir Putin by phone on Saturday.
• The phone call will be the first time the two leaders have directly spoken this year.

President Joe Biden is due to speak to his Russian President Vladimir Putin on Saturday, as US officials warn Russia could invade Ukraine within days.

Biden will speak to Putin by phone on Saturday morning, a White House official told Reuters, the first time the leaders have spoken directly since December 30.

Putin had requested the call with Biden take place on Monday, but the US president wanted to conduct it sooner amid fears that an invasion is imminent, The Guardian reported.

National security advisor Jake Sullivan said on Friday that there's a "credible prospect" Russia could invade Ukraine before the end of the Winter Olympics on February 20.

Biden reportedly told NATO and EU leaders in a private call on Friday that Vladimir Putin has decided to move forward with an invasion, The Guardian reported, citing diplomatic sources.

However, Sullivan said US intelligence does not know if Putin has decided about invading.

"I will say that the way that he has built up his forces and put them in place, along with the other indicators that we have collected through intelligence, makes it clear to us that there is a very distinct possibility that Russia will choose to act militarily, and there is reason to believe that that could happen on a reasonably swift timeframe," Sullivan said.

The Biden administration has told Americans in Ukraine to leave as soon as possible, and other countries, including Britain, Australia, and Japan, have urged their citizens to do the same.

On Saturday, the US State Department also ordered most of its American staff at its embassy in Kyiv to leave "due to the continued threat of Russian military action."

The State Department had already ordered family members of embassy staff to leave.

Sullivan warned that a Russian invasion would likely begin with aerial bombing and missile attacks that could kill civilians of all nationalities.

The Kremlin has claimed that it does not plan to invade, despite its aggressive posturing towards Ukraine.

For weeks, Russia has been amassing troops around Ukraine's border, with the number now reaching roughly 130,000.

The increasing tensions come around eight years after Russia invaded Ukraine and annexed Crimea. Since then, Russia has supported rebels in a war against Ukrainian forces in the eastern Donbas region.

The Kremlin has said it wants to enforce "red lines" to make sure that Ukraine does not join NATO.