Pretty sure the US is sending old surplus stock, and I'm sure the military industrial complex is salivating at the chance to resupply. Maybe if they send slightly newer stuff it might be over quicker.
At any rate, US support for exactly this type of situation was agreed on in the Budapest memorandum as part of Ukrainian nuclear disarmament. Russia broke their end of the bargain and started a war under false pretenses. It is up to them to end it, exactly like it is up to the US to do so when doing the same thing.
If the world can not unite to stand up to countries starting such conflicts, we shall never know peace.