The Secretary is authorized, upon such terms and conditions as the Secretary may prescribe, to guarantee and make commitments to guarantee, only to such extent or in such amounts as provided in appropriation Acts, the notes or other obligations issued by eligible public entities, or by public agencies designated by such eligible public entities, for the purposes of financing (1) acquisition of real property or the rehabilitation of real property owned by the eligible public entity (including such related expenses as the Secretary may permit by regulation); (2) housing rehabilitation; (3) economic development activities permitted under paragraphs (14), (15), and (17) of section 5305(a) of this title; (4) construction of housing by nonprofit organizations for homeownership under section 1437o(d) ^[1] of this title or title VI of the Housing and Community Development Act of 1987; (5) the acquisition, construction, reconstruction, or installation of public facilities (except for buildings for the general conduct of government); or (6) in the case of colonias (as such term is defined in section 916 of the Cranston-Gonzalez National Affordable Housing Act), public works and site or other improvements. A guarantee under this section may be used to assist a grantee in obtaining financing only if the grantee has made efforts to obtain such financing without the use of such guarantee and cannot complete such financing consistent with the timely execution of the program plans without such guarantee. Notes or other obligations guaranteed pursuant to this section shall be in such form and denominations, have such maturities, and be subject to such conditions as may be prescribed by regulations issued by the Secretary. The Secretary may not deny a guarantee under this section on the basis of the proposed repayment period for the note or other obligation, unless the period is more than 20 years or the Secretary determines that the period causes the guarantee to constitute an unacceptable financial risk. Notwithstanding any other provision of law and subject only to the absence of qualified applicants or proposed activities and to the authority provided in this section, to the extent approved or provided in appropriation Acts, the Secretary shall enter into commitments to guarantee notes and obligations under this section with an aggregate principal amount of $2,000,000,000 for fiscal year 1993 and $2,000,000,000 for fiscal year 1994. Of the amount approved in any appropriation Act for guarantees under this section in any fiscal year, the Secretary shall allocate 70 percent for guarantees for metropolitan cities, urban counties, and Indian tribes and 30 percent for guarantees for units of general local government in nonentitlement areas. The Secretary may waive the percentage requirements of the preceding sentence in any fiscal year only to the extent that there is an absence of qualified applicants or proposed activities from metropolitan cities, urban counties, and Indian tribes or units of general local government in nonentitlement areas.