The governing body of the Gila River Indian Community has voted unanimously to appeal a federal court's decision to allow construction of the proposed South Mountain Freeway adjacent to tribal lands.
Tribal officials say the project will desecrate lands held sacred by community members for centuries.
The U.S. District Court in Phoenix dismissed legal challenges on Aug. 19.
The court ruled that the Arizona Department of Transportation and Federal Highway Administration completed all steps required to move forward on the freeway.
ADOT officials say construction could start next month with the 22-mile freeway projected to open by late 2019 and connect Interstate 10 in Chandler and Laveen.
The tribe says its legal team also will seek an injunction to stop construction while their appeal is pending.