Putin has had every chance to start it already and continued as usual.
Putin is not going to change his mind because of Abrams tanks.
The West can send in all the aid it wants short of combat personnel and nukes, and Putin has no option for stopping it.
Nothing short of an existential threat to all of Russia will change any of this.
If you don’t believe this by this point in the war, I don’t know what else to tell you. He’s had plenty of chances and done nothing but complain. WW3 is not on the table.