Putin claims we're already in one. Their military is crumbling. Create some safe air corridors in Ukraine to supply the cities, just like we did with Berlin in the cold war.

Also, he's shown too many cards. His military is incompetent and/or looting itself.

Probably better to announce we're going to do this unless he "clairifes" his position.

Edit: Also, his strategy only works if the US behaves rationally, and also assumes that he will not behave rationally because he's senile and dying of cancer. Call (his subbordinates') bluff by making it clear Biden's battier than Regan.