41 USC 122 - Use of appropriated funds

Any contracting agency is authorized
(a) to use for interim financing, the payment of claims, and for any other purposes authorized in this chapter any funds which have heretofore been appropriated or allocated or which may hereafter be appropriated or allocated to it, or which are or may become available to it, for such purposes or for the purposes of war production or war procurement;
(b) to use any such funds appropriated, allocated, or available to it for expenditures for or in behalf of any other contracting agency for the purposes authorized in this chapter; and
(c) to determine by agreement, joint estimate, or any other method authorized by the Administrator of General Services, the part of any expenditure made pursuant to subsection (b) of this section to be paid by each contracting agency concerned and to make transfers of funds between such contracting agencies accordingly. Transfers of funds between appropriations carried upon the books of the Treasury shall be made by the Administrator of General Services in accordance with joint requests of the contracting agencies involved.