The park district has the power to secure grants and loans, or either, from the United States Government, or any agency thereof, for financing the planning, establishment and construction, enlargement and improvement of any harbor or any part thereof, authorized by this law. For such purposes it may issue and sell or pledge to the United States Government, or any agency thereof, all or any part of the revenue bonds authorized under this law, and execute contracts and documents and do all things that may be required by the United States Government, or any agency thereof, provided that such contracts and documents do not conflict with the provisions of any ordinance authorizing and securing the payment of outstanding bonds of the park district theretofore issued that are payable from the revenues derived from the operation of the harbor or facilities.