Russia invasion of Ukraine could come soon -Sullivan

"We have to be prepared for the possibility of a contingency of a military action by Russia before the Olympics end. And we also have to be prepared for one after the Olympics end. So at this point, we are in the window, meaning that we can't just assume it's going to be a couple of weeks off." Sullivan, who gave a round of television interviews, told ABC 'This Week with George Stephanopoulos'.

"The United States, under the direction of President Biden, are ready either way, We are ready if President Putin chooses to continue to engage in diplomacy and we are serious about that," Sullivan added.

Russia has in place about 70% of the combat power it believes it would need for a full-scale invasion of Ukraine and is sending more battalion tactical groups to the border with its neighbor, two U.S. officials said on Saturday.

As Russia masses more than 100,000 troops near the border, Moscow has said it is not planning an invasion but could take unspecified military action if its security demands are not met. Those include a promise that NATO will never admit Ukraine, a demand the United States and NATO have called unacceptable.