Congress controls expenditures already. The president is required make all appropriated funds available to the programs in question. Now technically the program

Congress controls expenditures already. The president is required make all appropriated funds available to the programs in question. Now technically the programs are allowed not to spend all the appropriated money, but that is up to those running that program, and as a general rule those programs will spend all the money, to within a rounding error. If the president were to issue orders to agencies to not spend all appropriated money on specific programs that would be considered "impoundment", which was prohibited by the Impoundment Control Act of 1974. Congress also largely controls revenue. The overwhelming majority of revenue is taxes. There is little that the president can do to significantly change the revenue received. [1] Since congress has left a deliberate deficit, the president is left with no choice but to issue more debt to make up that shortfall. But the debt ceiling would prevent that. The classical thinking (for some reason) is that if the debt ceiling is hit, the president will be forced not to pay the interest on the debt, since the appropriations are mandatory. This is the view that sees the debt ceiling itself as questionably constitutional, viewing the act of appropriating more than expected revenues to be authorizing the issuance of debt. Unfortunately it is also a wrong view. The correct view is that it is the Impoundment Control Act of 1974 that is unconstitutional, and that upon hitting the debt ceiling the President is obligated to impound appropriations as needed to avoid going over the debt ceiling. The result would probably be a partial government shutdown, similar to what happens when congress fails to pass an appropriation bill. This, of course, only works if the revenue received still exceeds the required interest payments on the debt. ----- Footnote: [1] The treasury cannot even print more paper money, since that is up the federal Reserve for Federal Reserve Notes, and while U.S. Notes are technically still authorized, Congress has set a limit of $300,000,000 U.S. Notes. It could mint more coins and deposit them with fed, but manufacturing costs are appropriated funds, and it is not possible to mint enough normal coins with the appropriated amounts to make a dent. Many coins (including the penny, and the >$1 precious metal ones cost more to make then their face value). Hence why the trillion dollar coin proposal used a platinum coin, which is the only category where the Treasurer gets to pick the size design and face value.