Alexander Vindman: US can stop the horror of a Putin war in Ukraine. But time is running out.

As Vladimir Putin continues to amass troops on the border of Ukraine, there is a growing sense that the die has been cast, and that invasion is unavoidable. President Joe Biden, in a news conference last week, said, "My guess is he will move in. He has to do something."

That may be true, but it does not mean we cannot further complicate Putin’s calculus while we still have a chance. At minimum, doing so could delay an invasion, giving Ukraine more time to prepare.