Pursuant to the agreement concluded under the authority of section 277d-32 of this title, the United States Commissioner is authorized to construct, operate, and maintain the portion of the “International Flood Control Project, Tijuana River Basin,” assigned to the United States, and there is hereby authorized to be appropriated to the Department of State for use of the United States section the sum of $10,800,000 for construction costs of such project, as modified, based on estimated June 1976 prices, plus or minus such amounts as may be justified by reason of price index fluctuations in costs involved therein, and such sums as may be necessary for its maintenance and operation, except that no funds may be appropriated under sections 277d-32 and 277d-33 of this title for the fiscal year ending on September 30, 1977. Contingent upon the furnishing by the city of San Diego of its appropriate share of the funds for the acquisition of the land and interests therein needed to carry out the agreement between the United States and Mexico to construct such project, the Secretary of State, acting through the United States Commissioner, is further authorized to participate financially with non-Federal interests in the acquisition of said lands and interest therein, to the extent that funds provided by the city of San Diego are insufficient for this purpose.