Once again, Congress has the power to head off the Doofus-in-Chief at the pass by simply passing an appropriation for these funds. Just like the sanctions bill, it could be passed with a veto-proof majority.
Once the payments are appropriated, the President can’t withhold them. Nixon did so much withholding of appropriated funds that Congress passed the Congressional Budget and Impoundment Control Act of 1974, which prohibits the President from impounding (withholding) funds appropriated by Congress for a specific purpose.