(a) (4) Commercial vehicle lease sources may be used only when the General Services Administration (GSA) has advised that it cannot furnish the vehicle(s) through the Interagency Motor Pool System and it has been determined that the vehicle(s) are not available through the GSA Consolidated Leasing Program. All subsequent lease renewals or extensions may be exercised only when GSA has advised that it cannot furnish the vehicle(s) as prescribed herein.