22 U.S.C. § 1479

If any other government shall express the desire to provide funds, property, or services to be used by this Government, in whole or in part, for the expenses of any specific part of the program undertaken pursuant to this chapter, the Secretary is authorized, when he finds it in the public interest, to accept such funds, property, or services. Funds so received may be established as a special deposit account in the Treasury of the United States, to be available for the specified purpose, and to be used for reimbursement of appropriations or direct expenditure, subject to the provisions of this chapter. Any unexpended balance of the special deposit account and other property received under this section and no longer required for the purposes for which provided shall be returned to the government providing the funds or property.