14 C.F.R. § 151.29 – Procedures: Offer, amendment, and acceptance.

(a) Upon approving a project, the Administrator makes an offer to the sponsor to pay the United States share of the allowable project costs. The offer states a definite amount as the maximum obligation of the United States, and is subject to change or withdrawal by the Administrator, in his discretion, at any time before it is accepted.
(b) If, before the sponsor accepts the offer, it is determined that the maximum obligation of the United States stated in the offer is not enough to pay the United States share of the allowable project costs, the sponsor may request an increase in the amount in the offer, through the Area Manager.
(c) An official of the sponsor must accept the offer for the sponsor within the time prescribed in the offer, and in the required number of counterparts, by signing it in the space provided. The signing official must have been authorized to sign the acceptance by a resolution or ordinance adopted by the sponsor's governing body. The resolution or ordinance must, as appropriate under the local law—
1. (1) Set forth the terms of the offer at length; or
2. (2) Have a copy of the offer attached to the resolution or ordinance and incorporated into it by reference.
  The sponsor must attach a certified copy of the resolution to each executed copy of an accepted offer or grant agreement that it is required to send to the Area Manager.