(a) The United States Governor is authorized to agree on behalf of the United States to pay to the Association $3,240,000,000 as the United States contribution to the sixth replenishment of the resources of the Association: Provided, however, That any commitment to make such contributions shall be made subject to obtaining the necessary appropriations.

(b) In order to pay for the United States contributions provided for in this section, there is authorized to be appropriated, without fiscal year limitation, $3,240,000,000 for payment by the Secretary of the Treasury: Provided, however, That not more than $850,000,000 of such sum may be made available for the fiscal year 1982 and not more than $945,000,000 of such sum may be made available for the fiscal year 1983.