The sources from which such funds can be ( b) borrowed are limited to voluntary-funded trust funds of organizations within the United Nations system, provided that the borrowing of such moneys shall be made with the agreement, where appropriate, of the executive directors of the voluntary funds and shall in no way adversely affect the operations of the trust funds to which the moneys have been contributed or the speedy implementation of the programmes concerned, it being understood that borrowings shall be made, in the first instance, from trust funds under the aegis of the Governing Council;