In case contract has been or may hereafter be made with the United States as herein provided, in lieu of the sale of bonds provided in section 43-409[, Idaho Code], bonds of the district may be deposited with the United States at ninety per cent (90%) of their par value, to the amount to be paid by the district to the United States under any such contract, the interest on said bonds to be provided for by assessment and levy as in the case of other bonds of the district, and regularly paid to the United States to be applied as provided in such contracts.