Effective July 1, 1974, no defense article shall be furnished to any country on a grant basis unless such country shall have agreed that the net proceeds of sale received by such country in disposing of any weapon, weapons system, munition, aircraft, military boat, military vessel, or other implement of war received under this part will be paid to the United States Government and shall be available to pay all official costs of the United States Government payable in the currency of that country, including all costs relating to the financing of international educational and cultural exchange activities in which that country participates under the programs authorized by the Mutual Educational and Cultural Exchange Act of 1961 [
22 U.S.C.
2451 et seq.]. In the case of items which were delivered prior to 1985, the President may waive the requirement that such net proceeds be paid to the United States Government if he determines that to do so is in the national interest of the United States.