((a)) ** .—** In a case in which a proposed Federal-aid project is to be undertaken by a Federal agency in accordance with an agreement between a State and the Federal agency, the State may—

((1)) direct the Secretary to transfer the funds for the Federal share of the project directly to the Federal agency; or

((2)) make such deposit with, or payment to, the Federal agency as is required to meet the obligation of the State under the agreement for the work undertaken or to be undertaken by the Federal agency.

((b)) ** .—** On execution with a State of a project agreement described in subsection (a), the Secretary may reimburse the State, using any available funds, for the estimated Federal share under this title of the obligation of the State deposited or paid under subsection (a)(2).

((c)) ** .—** Any sums reimbursed to the State under this section which may be in excess of the Federal pro rata share under the provisions of this title of the State’s share of the cost as set forth in the approved final voucher submitted by the State shall be recovered and credited to the same class of funds from which the Federal payment under this section was made.