Biden National Security adviser Jake Sullivan told NBC News this morning that Russia shows no signs of pulling back and says the coming invasion of Ukraine by Russian forces, "expected within hours or days," will be exceptionally brutal, including the detention and killing of Ukrainian civilians.

"But we also have intelligence to suggest that there will be an even greater form of brutality. Because this will not simply be some conventional war between two armies. It will be a war waged by Russia on the Ukrainian people to repress them, to crush them, to harm them. And that is what we laid out in detail for the U.N., because we believe that the world must mobilize to counter this kind of Russian aggression should those tanks roll across the border, as we anticipate they very well may do in the coming hours or days," he said.

"Jake, we are convinced that Russia will invade Ukraine. What leads you to believe that they are going to stop at Ukraine?"

"Well, the most important thing that the president has done with respect to deterrence has been to send thousands of American service members to Poland and Romania and to work with other allies to send forces to NATO allies along NATO's east, the areas that border Ukraine or border Russia. So he has been absolutely clear, the president, that we will defend every inch of NATO territory because we have an article 5 commitment to do so, and that is a sacred obligation.

"And if Russia chooses to move against any NATO country, come further west into NATO territory, they will be met with the full force of American and allied might," Sullivan said.

And this update: