The Foreign Aid and Related Agencies Appropriation Act, 1963, and subsequent appropriation Acts, have imposed the following requirement:

None of the funds appropriated or made available pursuant to this Act for carrying out the Foreign Assistance Act of 1961, as amended, may be used for making payments on any contract for procurement to which the United States is a party entered into after the date of enactment of this Act which does not contain a provision authorizing the termination of such contract for the convenience of the United States.

See, for example, section 110 of the Foreign Assistance and Related Agencies Appropriation Act, 1965.