When, in the opinion of the Secretary of the Army, it is in the interest of the United States so to do, he is authorized to enter into contracts and to incur obligations for fuel in sufficient quantities to meet the requirements for one year without regard to the current fiscal year, and payments for supplies delivered under such contracts may be made from funds appropriated for the fiscal year in which the contract is made, or from funds appropriated or which may be appropriated for such supplies for the ensuing fiscal year