(b) The sum of two million five hundred thousand dollars ($2,500,000), or so much thereof as may be necessary, is hereby appropriated in the first instance out of any moneys in the state treasury in the general fund to the credit of the state purposes fund, not otherwise appropriated, to the Niagara thruway toll removal fund for the purposes of this article. No part of the appropriation hereby made shall be available until a certificate of approval of availability shall have been issued by the director of the budget and a copy of such certificate filed with the state comptroller, the chairman of the senate finance committee and the chairman of the assembly ways and means committee. Such certificate may be amended from time to time by the director of the budget and a copy of each such amendment shall be filed with the state comptroller, the chairman of the senate finance committee and the chairman of the assembly ways and means committee. 2. The fund shall pay over annually from moneys made available to it from any source to the New York state thruway authority an amount equal to an amount sufficient to amortize that portion of the debt service of the authority allocable to the Niagara section of said thruway authority; provided, however, an agreement shall be entered into between the fund, the commissioner of transportation, the thruway authority and the bureau of public roads of the United States department of transportation providing: for the aforesaid annual payments by the fund to the thruway authority; that the federal government make the payments provided under paragraph (a) of subdivision one of this section; that such tolls shall be removed as of the time of the first of such payments to the thruway authority; that such tolls shall not be collected so long as such annual payments are made; and further that the thruway authority shall operate and maintain such section in the same manner as on the sixth day of July, nineteen hundred sixty-six.