Biden and Putin to speak Thursday amid tensions over Ukraine

President Biden and Russian President Vladimir Putin will speak on the phone on Thursday, the White House said Wednesday. The call was requested by Putin, a White House official said.

The White House said the two leaders will discuss "a range of topics, including upcoming diplomatic engagements with Russia," although a senior administration official said the call will be focused on concerns Russia's troop presence along the Ukrainian border.

The senior administration official said "we're in a moment of crisis" about Russia's buildup of troops near the border with Ukraine, and "it will take a high level of engagement to address this and find a path of de-escalation."

On Thursday's call, the official said Mr. Biden will make clear he's prepared for a diplomatic path forward to reducing tensions, but also that "we're prepared to respond" if Russia advances with a further invasion of Ukraine, including with coordinated economic sanctions, "further assistance" to Ukraine and steps to "reinforce NATO's force posture." 

The two leaders held a video call earlier this month, with Mr. Biden telling Putin he had "deep concerns" about the troop buildup. The White House said Mr. Biden told Putin the U.S. would pursue "strong economic and other measures" in the event of an invasion.

The White House said on Wednesday that Mr. Biden continues to coordinate with European allies for "a common approach in response to Russia's military build-up on the border with Ukraine." 

U.S. Secretary of State Antony Blinken on Wednesday met with Ukrainian President Volodymyr Zelenskyy. State Department spokesperson Ned Price said Blinken "reiterated the United States' unwavering support for Ukraine's independence, sovereignty, and territorial integrity in the face of Russia's military buildup on Ukraine's borders."

The senior administration official said Wednesday there is no plan so far for Mr. Biden to speak to Zelenskyy after the Putin call like he did last time, but they are expected to speak soon.

U.S. intelligence has warned that Russia could invade Ukraine as early as January, a U.S. official told CBS News earlier this month. Russia has built up an estimated 100,000 troops near the Ukrainian border. Despite recent reports that the Russians have withdrawn 10,000 troops from the area, the senior administration official said the White House is "greatly concerned" about the still "significant Russian troop presence" along the border. CBS News has reported that the 10,000 withdrawn troops is just a fraction of the number that still remains at the border.

In 2014, Russia annexed Ukraine's Crimean peninsula and amassed troops along the border. 

Kristin Brown contributed to this report.