From all the posturing that he has done lately, he has to, if he doesn't, his credibility will take a hit
And the americans will sense a weakness
The million dollar question is when?
Why? He never declares either explicitly or implicitly that Russia was or is going to invade Ukraine. The west led by America have been shouting about a Russian invasions since 2014 and it has yet to materialize.
The one thing that Russia has been consistent about is NO NATO expansion that even that drunkard Yeltsin also opposed but his Russia at that time was too weak to make a stink about it.
It's the west utter lack of respect and vitriolic hatred for Russian nationalism that's caused this issue regardless of one likes Putin or not. No self-respecting Russian citizen would want his or her country be dictated, humiliated, and essentially become another vassalized country to the primacy and interests of the Anglo-west which is what the U.S. has been trying to do since the end of the Cold War.
The U.S. and her vassals can renege and lie on their prior commitments, can make up new rules ad hoc and abuse the international laws and international institutions pretty much getting away risks free. Meanwhile, countries like Russia, China and others can't even dare to sneeze without getting pilloried, despise, sanctioned, and accused of pretty much all the heinous things one can be attached to a state.
The U.S. doesn't want to be challenged in any sphere any territories it wish to operate full stop. It wants and loves to dictate what the rules of the road and the game are to it's own distinct advantages/national interests to the detriment of international order and laws.