25 CFR §224.116

1. (a)If the Secretary determines under § 224.115 that one of the threshold determinations in § 224.114 has been met, then within 120 days of the Secretary's receipt of a petition, the Secretary must determine:
   1. (1)Whether the petitioner is an interested party; and
   2. (2)If the petitioner is an interested party, whether or not a Tribe is in compliance with the TERA as alleged in the petition;
2. (b)The Secretary may extend the time for the Tribe making the determinations in paragraph (a) of this section for up to 120 days in any case in which the Secretary determines that additional time is necessary to evaluate the claims in the petition and the Tribe's written response, if any. If the Secretary decides to extend the time, the Secretary must notify the petitioner and the Tribe in writing of the extension.