US president Joe Biden and Russian president Vladimir Putin will speak on Thursday, the White House said, as Washington crafts a common response to Russia's military build-up on the Ukraine border with European allies.
The two leaders will discuss a range of topics, including upcoming security talks between the countries and a tense situation in Europe, White House National Security Council spokesperson Emily Horne said in a statement.
Kremlin spokesman Dmitry Peskov told Reuters the call was planned for "late Thursday evening," without elaborating.
Ms Horne said Mr Biden had spoken with leaders across Europe about the situation on the Ukraine border, while Biden administration officials were in touch with NATO, the European Union and the Organisation for Security and Cooperation in Europe.
Moscow has alarmed the West by massing tens of thousands of troops near Ukraine in the past two months, following its seizure of Ukraine's Crimea peninsula in 2014 and its backing of separatists fighting Kyiv troops in eastern Ukraine.
Russia denies planning to attack Ukraine and says it has the right to move its troops on its own soil as it likes.
Moscow, worried by what it says is the West's re-arming of Ukraine, has said it wants legally-binding guarantees NATO will not expand further eastwards, and that certain offensive weapons will not be deployed to Ukraine or other neighbouring countries.
US concerns have not ebbed in recent weeks, according to a senior Biden administration official. Other US officials said that despite a report over the weekend that Russia would be pulling back about 10,000 troops from its border with Ukraine, they had seen little evidence to support that so far.
"We are at a moment of crisis and have been for some weeks now given the Russian build-up, and it will take a high level of engagement to address this and to find a path of de-escalation," said one of the officials, who declined to be named.
That person said Mr Putin requested the call with Mr Biden.
"When President Biden has asked to speak with President Putin over the course of 2021, President Putin has said, Yes, let's talk. And when President Putin says, I'm interested in touching base and having a phone call, President Biden says yes."
Mr Biden is likely to reiterate during the call that the United States will take swift economic action against Russia in the case of an invasion. They will also reinforce the North Atlantic Treaty Organisation in such a case.
But the US president has been pushing direct diplomacy as an alternative.
The Biden administration has been in deep talks with Ukraine as well as a host of NATO allies, including those bordering Russia, according to Ms Horne, the White House spokesperson.
Mr Biden will likely speak with Ukraine's president Volodymyr Zelenskiy soon, another official said. US Secretary of State Antony Blinken spoke with the Ukrainian leader on Wednesday and expressed "unwavering support for Ukraine's independence," according to a spokesperson.
JSTARS, a type of US military spy plane, operated in Ukrainian airspace for the first time earlier this week, though different types of surveillance aircraft are common in the region, officials said.
Mr Biden on Tuesday said "we'll see" when asked if he would meet Mr Putin on January 10th, the same day US and Russian officials are due to hold security talks. But Mr Biden is not expected to attend those talks or meet with Mr Putin that day, an official said.
Russia and NATO are also set to hold talks on January 12th, with a broader meeting including Moscow, Washington and other European countries slated for January 13th.
Mr Putin has compared to the current tensions to the Cold War-era Cuban Missile Crisis in 1962. Washington regards some of his demands, including restrictions on NATO expansion, as non-starters.
Conversations between Mr Putin and Mr Biden are likely to touch on other issues, too, including the ongoing talks with Iran over its nuclear programme, a US official said.