If and when an association is a member of a Federal Home Loan Bank, it shall have power to act as fiscal agent of the United States, and, when so designated by the Secretary of the Treasury, it shall perform, under such regulations as he may prescribe, all such reasonable duties as fiscal agent of the United States as he may require, and when authorized shall have power to act as fiscal agent for any instrumentality of the United States or of any instrumentality of this State.