Trump : declare a national emergency and halt all discretionary spending.
Reportedly, Trump is planning to go the impoundment route, where the president can not use certain monies spent by Congress...or not use all of it.
Certain to be challenged in court but it’s been done before by previous presidents.
“Impoundment is a deliberate action by the President [2] to withhold some funding that Congress has enacted in an appropriations bill, so that not all of it would be used during the period for which it is made available.”