You don't want to shoot your relatives in another country and you are afraid to meet the same fate as your general killed from a long distance because crazy politician in power had a tantrum?.
The solution is simple: Some pieces in your tank broke, you turn in the wrong direction and get stuck in a marsh, or gasoline vanish mysteriously overnight and you are stuck out of the war until a replacement arrives with the spare parts.
This can lasts for several weeks or months if you must buy it in another countries and nobody is selling you. Or can need to fill a lot of bureaucracy to just take if from another tank and send it to the front (and then you have 2 tanks out of service instead one). When you finally arrive to the fight there is a lot less of enemies to deal with.
With the advantage that you didn't deserted and don't fear retaliation. You can blame the tank maker or any other that is lower in the food chain. It was not your fault.
"Backed into a corner" is a phrase that is tossed around too easily these days. NATO does not want to force him into that corner with a "no-fly" zone over Ukraine. Brutal, backbreaking sanctions and the loss of support of a brainwashed public is the current alternative. I am certain that there are even harsher options in the pipeline. For example, cutting off oil and gas purchases, and sacrificing Western economies in an era of record high inflation. In my opinion, NATO will gladly make that trade to keep Putin from abandoning MAD.
I suppose you were being sarcastic, but put away your snide and come up with actual better suggestions!