This is not some business deal where you can change terms later on and let the courts decide. Turkey needs to know if NATO will be there for them or not. He can call for larger contributions of course and tell them upfront that NATO won't help them until conditions are met. But he can't decide at the time Russia invades. Then he may as well leave NATO.

Trump was also a "birther". That alone shows to me that he doesn't take politics seriously.