In order to assist nonprofit private agencies to carry out needed projects for the modernization or construction of nonprofit private hospitals, facilities for long-term care, outpatient facilities, and rehabilitation facilities, the Secretary, during the period July 1, 1970, through June 30, 1974, may, in accordance with the provisions of this part, guarantee to non-Federal lenders making loans to such agencies for such projects, payment of principal of and interest on loans, made by such lenders, which are approved under this part.