Notwithstanding any other provision of law, the Commodity Credit Corporation, with the approval of the President, is authorized to sell surplus agricultural commodities, acquired by such Corporation through its loan operations, to foreign governments on the condition that, except for rotation to prevent deterioration, such commodities shall be held in reserve by such governments for a period of not less than five years from the date of acquisition, and shall not be disposed of unless a war or war emergency results in a serious interruption of normal supplies of such commodities: Provided, That under this section no concession below the prevailing world market price for the unrestricted use of such commodities, as determined by the Secretary of Agriculture, shall be granted, in consideration of the obligation assumed by such governments to hold such commodities in reserve as required hereinbefore, in excess of a maximum amount equal to the average carrying charges, as estimated by the Secretary of Agriculture, that would be incurred if such commodities should be held for an additional eighteen months’ period by the Commodity Credit Corporation. In determining specific cotton to be sold under this section, the determination shall be made by sampling and selection at the place where the cotton is stored on the date of signing any sales agreement or contract under this section, and no cotton shall be sold under any such sales agreement or contract which, after such date, is transported to any other place and there sampled and selected: Provided further, That in case of a sale, settlement must be made within sixty days after delivery and not more than five hundred thousand bales of cotton shall be sold upon the terms and conditions provided in this section.