- Any Americans still in Ukraine should leave "immediately," the White House said.
- Russia could potentially launch an invasion of the country "any day now," said President Joe Biden's national security advisor, Jake Sullivan.
- Biden plans to hold a call with Putin on Saturday, a senior official told CNBC.
Any Americans still in Ukraine should leave "immediately," the White House said Friday, as it warned that Russia could potentially launch an invasion of the country "any day now" — possibly even during the Olympics.
"Any American in Ukraine should leave as soon as possible, and in any event in the next 24 to 48 hours," President Joe Biden's national security advisor, Jake Sullivan, said during a press briefing.
Those remarks echoed Biden's own warning Thursday for U.S. citizens in Ukraine to "leave now."
"This is a very different situation, and things could go crazy quickly," Biden said during an interview with NBC News' Lester Holt.
On Saturday, Biden will hold a one-on-one call with Russian President Vladimir Putin, a White House official told CNBC. French President Emmanuel Macron will also speak with Putin that day, CNBC has learned.
Russian Foreign Minister Sergei Lavrov, during a phone call with U.S. Secretary of State Antony Blinken, accused Washington of waging a "propaganda campaign" about possible Russian aggression, the Russian foreign ministry said on Saturday.
In a readout of Saturday's phone call with Blinken, Lavrov also said Washington and Brussels have ignored key Russian security demands.
U.S. national security advisor Sullivan noted that the U.S. is not certain that Putin has made a final decision to invade Ukraine. But "it may well happen soon," he said.
On Friday, a senior Defense Department official told NBC News that Secretary Lloyd Austin has ordered another 3,000 American troops to deploy to Poland over the weekend.
They are expected to be in place by early next week, the official said. This latest tranche of troops will join the approximately 2,000 troops already deployed to Europe this month.
Russia has spent months building up its military presence at various points along the Ukrainian border. More than 100,000 Russian troops are currently stationed there.
Russia has now positioned about 80% of the forces required for a full-scale invasion of Ukraine, a Western intelligence official and a U.S. official told NBC.
An invasion, if it occurs, was previously expected to come after the close of the Winter Olympics in Beijing in order to avoid a conflict with China, Russia's ally.
The 2022 Winter Games, set to end on Feb. 20, have been marred by controversy, including diplomatic boycotts over China's human rights record and the recent revelation that a champion Russian figure skater failed a drug test.
But Sullivan on Friday stressed that an attack "could begin during the Olympics, despite a lot of speculation" that it would not.
Should Russia invade, the U.S. and its allies are "ready to respond decisively" through an array of actions, such as imposing "severe economic sanctions" and changes to NATO's force posture, Sullivan said.
"If Russia proceeds, its long-term power and influence will be diminished, not enhanced, by an invasion," Sullivan said.
"It will face a more determined transatlantic community. It will have to make more concessions to China. It will face massive pressure on its economy and export controls that will erode its defense industrial base, and it will face a wave of condemnation from around the world," he said.
"Whatever happens next, the West is more united than it's been in years," Sullivan said.
Biden earlier Friday held a video call with several NATO leaders to discuss the Kremlin's escalation on the Russia-Ukraine border.
On it, the leaders "agreed on the importance of coordinated efforts to deter further Russian aggression against Ukraine, including their readiness to impose massive consequences and severe economic costs on Russia should it choose military escalation, and to continue reinforcing the defensive posture on NATO's eastern flank," according to a White House readout of the call.
Other countries, including Britain and Israel, have also urged their citizens to leave Ukraine.
—CNBC's Kayla Tausche and Reuters contributed to this report.