(a) The Postal Service may offset against any balances due another country resulting from the transaction of international money order business, or otherwise, amounts due from that country to the United States, or to the United States for the account of air carriers of the United States transporting mail of that country, when—
the Postal Service puts into effect rates of compensation to be charged another country for transportation; and
(b) When the Postal Service has proceeded under authority of subsection (a) of this section, it shall—
(c) The Postal Service may advance to an air carrier, out of funds available for payment of balances due other countries, the amounts determined by the Postal Service to be due from another country to an air carrier for the transportation of its mails when—
the Postal Service determines that the balance of funds available is such that the advances may be made therefrom.
Collection from another country of the amount so advanced shall be made by offset, or otherwise, and the appropriation from which the advance is made shall be reimbursed by the collections made by the United States.
The Postal Service shall adopt such accounting procedures as may be necessary to conform to and carry out the purposes of this section.