Despite applauding at Joe Biden's ascendency to President of the United States, I am puzzled by the lack of political savvy he displayed before Russia invaded Ukraine.

One week before the invasion he was asked to comment about Russia's critical issue to avert an upcoming invasion—with ground troops movements for which he was privy and which he chose to make public.

His response was "the Russians are asking for something [excluding Ukraine from membership in NATO] they know they cannot get."

We assume that a politician should always say "maybe". Had Biden said "maybe", and then engaged into highly confidential discussions between NATO and Ukraine, they could have announced overnight that Ukraine had become a NATO member.

Putin would not have dared invade, just like he has not dared invade Estonia, Latvia, or Lithuania, former Soviet countries that have long (since 2004) been NATO members. Having an open water route through their access to the Baltic Sea, Estonia, Latvia, and Lithuania pose a far more serious risk for Russia: NATO could more readily launch a strike on St Petersburg or Moscow from these states. But Putin knows that invading these three countries would be an invitation to WW3 that the US would find very hard to avoid.

What was the wisdom behind President Biden declining to put Ukraine's NATO membership on the negotiating table?

Edit

Several ways for asking the question in one sentence are possible:

• If merely saying 'maybe' (Ukraine will be Finlandized) would have spared Ukraine an invasion, why did President Biden not say it?
• More generally, what makes some politicians say 'absolutely not' (rather than maybe, conceivably, remotely) when the interlocutor is a powerful adversary? Isn't saying 'absolutely not' a recipe for inviting armed conflict?

If you're voting down, please indicate why. If you disagree with any premise of the question, express your disagreement as an answer. I welcome being proven wrong.

Edit 2

I have just found a hero in the person of John Mearsheimer. As far back as seven years ago he voiced a position not too different from the one in this question: that by refusing to negotiate with Russia about Ukraine, the US effectively is throwing (now threw) Ukraine under the Russian steamroller.

Mearsheimer uses an analogy with the Cuban missile crisis. Just as the US then categorically refused to allow the Soviets to position missiles so close to the US mainland (yet still far from the US capital), the Russians have been insensed at the prospect of having NATO set up a front line so close to Moscow.