(a) Except as provided in paragraphs (b) and (c) of this section, until an agency issues a finding of no significant impact, as provided in § 1501.6 of this subchapter, or record of decision, as provided in § 1505.2 of this subchapter, no action concerning the proposal may be taken that would:

(1) Have an adverse environmental effect; or

(2) Limit the choice of reasonable alternatives.

(b) If an agency is considering an application from an applicant and is aware that the applicant is about to take an action within the agency's jurisdiction that would meet either of the criteria in paragraph (a) of this section, then the agency shall promptly notify the applicant that the agency will take appropriate action to ensure that the objectives and procedures of NEPA are achieved. This section does not preclude development by applicants of plans or designs or performance of other activities necessary to support an application for Federal, State, Tribal, or local permits or assistance. An agency considering a proposed action for Federal funding may authorize such activities, including, but not limited to, acquisition of interests in land (e.g., fee simple, rights-of-way, and conservation easements), purchase of long lead-time equipment, and purchase options made by applicants, if the agency determines that such activities would not limit the choice of reasonable alternatives and notifies the applicant that the agency retains discretion to select any reasonable alternative or the no action alternative regardless of any activity taken by the applicant prior to the conclusion of the NEPA process.

(c) While work on a required environmental review for a program is in progress and an action is not covered by an existing environmental document, agencies shall not undertake in the interim any major Federal action covered by the program that may significantly affect the quality of the human environment unless such action:

(1) Is justified independently of the program;

(2) Is itself accompanied by an adequate environmental review; and

(3) Will not prejudice the ultimate decision on the program. Interim action prejudices the ultimate decision on the program when it tends to determine subsequent development or limit alternatives.