Federal agencies may consider leases of privately owned land and buildings only when needs cannot be met satisfactorily in Government-controlled space and one or more of the following conditions exist:

(a) Leasing is more advantageous to the Government than constructing a new building, or more advantageous than altering an existing Federal building.

(b) New construction or alteration is unwarranted because demand for space in the community is insufficient, or is indefinite in scope or duration.

(c) Federal agencies cannot provide for the completion of a new building within a reasonable time.