Native American tribes and Blockchains Financeenvironmentalists want a U.S. appeals court to weigh in on their request to halt construction along part of a $10 billion transmission line that will carry wind-generated electricity from New Mexico to customers as far away as California.

The disputed stretch of the SunZia Transmission line is in southern Arizona’s San Pedro Valley. The tribes and others argue that the U.S. Interior Department and Bureau of Land Management failed to recognize the cultural significance of the area before approving the route of the massive project in 2015.

SunZia is among the projects that supporters say will bolster President Joe Biden’s agenda for cutting greenhouse gas emissions. The planned 550-mile (885-kilometer) conduit would carry more than 3,500 megawatts of wind power to 3 million people.

A U.S. district judge rejected earlier efforts to stall the work while the merits of the case play out in court, but the tribes and other plaintiffs opted Wednesday to ask the 9th U.S. Circuit Court of Appeals to intervene.

The Tohono O’odham Nation has vowed to pursue all legal avenues for protecting land that it considers sacred. Tribal Chairman Verlon Jose said in a recent statement that he wants to hold the federal government accountable for violating historic preservation laws that are designed specifically to protect such lands.

He called it too important of an issue, saying: “The United States’ renewable energy policy that includes destroying sacred and undeveloped landscapes is fundamentally wrong and must stop.”

The Tohono O’odham — along with the San Carlos Apache Tribe, the Center for Biological Diversity and Archeology Southwest — sued in January, seeking a preliminary injunction to stop the clearing of roads and pads so more work could be done to identify culturally significant sites within a 50-mile (80.5-kilometer) stretch of the valley.

Attorneys for the plaintiffs have alleged in court documents and in arguments made during a March hearing that the federal government was stringing the tribes along, promising to meet requirements of the National Historic Preservation Act after already making a final decision on the route.

The motion filed Wednesday argues that the federal government has legal and distinct obligations under the National Historic Preservation Act and the National Environmental Policy Act and that the Bureau of Land Management’s interpretation of how its obligations apply to the SunZia project should be reviewed by the appeals court.

California-based developer Pattern Energy has argued that stopping work would be catastrophic, with any delay compromising the company’s ability to get electricity to customers as promised in 2026.

In denying the earlier motion for an injunction, U.S. Judge Jennifer Zipps had ruled that the plaintiffs were years too late in bringing their claims and that the Bureau of Land Management had fulfilled its obligations to identify historic sites and prepare an inventory of cultural resources. Still, she also acknowledged the significance of the San Pedro Valley for the tribes after hearing testimony from experts.