(1) If the [Central Government] apprehends that a protected monument is in danger of being destroyed, injured or allowed to fall into decay [the Central Government may direct the State Government to acquire it] under the provisions of the Land Acquisition Act, 1894 (1 of 1894), as if the preservation of a protected monument were a "public purpose" within the meaning of that Act.
(2) The powers of compulsory purchase conferred by sub-section (1) shall not be exercised in the case of--
(a) any monument which or any part of which is periodically used for religious observances; or
(b) any monument which is the subject of a subsisting agreement executed under section 5.
(3) In any case other than the cases referred to in sub-section (2) the said powers of compulsory purchase shall not be exercised unless the owner or other person competent to enter into an agreement under section 5 has failed, within such reasonable period as the Collector may fix in this behalf, to enter into an agreement proposed to him under the said section or has terminated or given notice of his intention to terminate such an agreement.