The Commonwealth does hereby pledge to and agree with any person or Federal agency subscribing to or acquiring the bonds to be issued by the authority for the construction of any project or part thereof, that the Commonwealth will not limit or alter adversely the rights hereby vested in the authority until all bonds at any time issued, together with the interest thereof, are fully met and discharged. The Commonwealth does further pledge to and agree with any Federal agency that if such Federal agency shall construct or contribute funds for the construction of any project or any portion thereof, the Commonwealth will not alter or limit the rights and powers of the authority in any manner which would be inconsistent with the continued maintenance and operation of any project or the improvement thereof, or which would be inconsistent with the due performance of any agreements between the authority and such Federal agency, and the authority shall continue to have and may exercise all powers herein granted, as long as the same shall be necessary or desirable for carrying out the purposes of this act and the purposes of the United States pertaining to the construction, acquisition or improvement of any project or such portion thereof.