Sullivan says threat of Russian military invasion of Ukraine 'high'

White House national security adviser Jake Sullivan said Thursday that the threat of a Russian military invasion of Ukraine is "high" and stressed that the U.S. and its European allies are prepared for "any contingency."

Sullivan described talks involving the U.S., NATO and Russia over the past week as "frank and direct" but said that there has not been an agreement between U.S. and Russian officials for more meetings or discussions. He said that the U.S. would consult with allies before determining the next steps.

"We will now reflect and consult with allies and partners on how to proceed," Sullivan said. "We're prepared to continue with diplomacy to advance security and stability in the Euro Atlantic. We are equally prepared if Russia chooses a different path."

The Biden administration has warned of punishing international sanctions on Russia should Russian President Vladimir Putin decide to stage a military invasion of Ukraine, and said that the U.S. would beef up its presence on NATO's eastern flank and send additional security assistance to Ukraine in the case of an invasion.

Sullivan Thursday said that the U.S. intelligence community has still not assessed that Putin has made up his mind on launching a military invasion of Ukraine, but he said the Biden administration is clear-eyed about the threat given the roughly 100,000 Russian troops amassed at Ukraine's border.

"It is certainly the case that the threat of military invasion is high," Sullivan said. "There is no illusions on the part of any of us who have been dealing with this issue about what the prospects are for potential conflict and potential military escalation by Russia."

"The United States and its European allies and partners are prepared for multiple eventualities," he added.

U.S. officials just wrapped up four days of talks with the Russians and NATO allies in Europe during which they tried to ward off military conflict in Ukraine. Deputy Secretary of State Wendy Sherman led the talks for the Biden administration.

There were no major breakthroughs in the discussions, but U.S. officials did propose working with Russia on reciprocal agreements to restrict missile placement and limit the size and scope of military exercises.

At the same time, the U.S. forcefully rejected Russia's desire to limit NATO's expansion so that it would not include Ukraine.

"We will not allow anyone to slam closed NATO's open door policy," Sherman said Monday following the extraordinary session of the Strategic Stability Dialogue with Russia.

Meanwhile, there are growing concerns about a Russian invasion on par with Putin's invasion and annexation of Ukraine's Crimean Peninsula in 2014.

Following the conclusion of the third diplomatic meeting on Thursday, Michael Carpenter, the U.S. ambassador to the Organization for Security and Cooperation in Europe (OSCE), warned of a pressing threat of war as Russians carry out live-fire drills near Ukraine.

"We're facing a crisis in European security. The drumbeat of war is sounding loud, and the rhetoric has gotten rather shrill," Carpenter told reporters.

Evelyn Farkas, who served as Deputy Assistant Secretary of Defense for Russia, Ukraine, and Eurasia during the Obama administration, estimated that there is a greater than 50 percent chance that Putin invades Ukraine.

"I find it hard to believe that he'll walk back from the brink because he didn't get anything fundamental from us," she said.

Farkas urged the U.S. to do more to rally the international community to prepare for war between Russia and Ukraine, arguing that such an effort is needed to get Russia to back down.

Sullivan reiterated on Thursday that any progress with the Russians would need to take place in an "environment of de-escalation," reiterating a call for Russia to pull back troops from the border with Ukraine.

"As I stand here today, I can't tell you what the next steps will be," Sullivan said. "I can only tell you that the United States, the Biden administration, our allies and partners, we're prepared to deal with whatever comes."

--Updated at 4:56 p.m.