President Joe Biden spoke to Ukrainian President Volodymyr Zelenskyy by phone Sunday, reaffirming U.S. support for Ukraine as it faces growing Russian aggression, the White House said.
Russia has built up 100,000 or so troops along the border with Ukraine, prompting fears of an invasion as early as this month. Russia has repeatedly denied that it plans to attack its neighbor, but Biden administration officials have said they are prepared for the possibility.
Biden told Zelenskyy that the U.S. and its allies and partners will "respond decisively" if Russia invades, White House press secretary Jen Psaki said in a statement.
"Biden underscored the commitment of the United States and its allies and partners to the principle of 'nothing about you without you,'" Psaki said. "He also expressed support for confidence-building measures to de-escalate tensions in Donbas and active diplomacy to advance the implementation of the Minsk Agreements, in support of the Normandy Format."
Zelenskyy praised the "unwavering support" in a tweet.
Russia and the U.S. have engaged in high-stakes diplomatic discussions over Ukraine in recent weeks.
Biden urged Putin to de-escalate tensions in a 50-minute phone call Thursday. Biden warned Putin that the U.S. could impose new sanctions if Russia takes military action against Ukraine. The call, the second between Biden and Putin last month, was requested by the Russians.
"We made it clear to President Putin that if he makes any more moves and goes into Ukraine, we will have severe sanctions. We will increase our presence in Europe with our NATO allies, and it will be a heavy price to pay for it," Biden told reporters in Wilmington, Delaware, on New Year's Eve.
Biden made similar remarks in a call with Putin in early December, when Biden said Moscow would face "severe consequences" if it moved on Ukraine.
Putin warned on the call that relations could be completely severed if Biden imposed sanctions, Kremlin aide Yury Ushakov told reporters Friday, according to the Russian news agency TASS.
In a phone call Wednesday with Zelenskyy, Secretary of State Antony Blinken reaffirmed U.S. support for Ukraine's independence, sovereignty and territorial integrity, State Department spokesperson Ned Price said in a statement.
"The two discussed efforts to peacefully resolve the conflict in eastern Ukraine and upcoming diplomatic engagements with Russia," he said.
U.S. and Russian officials are scheduled to hold security talks in Geneva on Jan. 10, which Biden and Putin are not expected to participate in. A meeting between Russia and NATO is scheduled for Jan. 12.