The state pledges to the United States or any agency thereof that if any federal agency shall construct, loan, or contribute any funds for the construction, extension, improvement, or enlargement of any redevelopment project, or any portion thereof, the state will not alter or limit the rights and powers of the department or the local agency in any manner inconsistent with the performance of any agreements between the department or the local agency and any such federal agency. The department and the local agency shall continue to have all powers herein granted, so long as the same shall be necessary or desirable for the carrying out of the purposes of these sections.