The Secretary under such regulations as he may prescribe, may sell to public and commercial vessels and other watercraft, such fuel, supplies and furnish such services as may be required to meet the necessities of the vessel or watercraft if such vessel or watercraft is unable—

(1) to procure the fuel, supplies, or services from other sources at its present location; and

(2) to proceed to the nearest port where they may be obtained without endangering the safety of the ship, the health and comfort of its personnel, or the safe condition of the property carried aboard.

Sales under this section shall be at such prices as the Secretary considers reasonable. Payment will be made on a cash basis or on such other basis as will reasonably assure prompt payment. Amounts received from such a sale shall, unless otherwise directed by another provision of law, be credited to the current appropriation concerned and are available for the same purposes as that appropriation.