US President Donald Trump's outgoing administration approved a land swap on Friday for a Rio Tinto copper mine in Arizona that would boost domestic production of the red metal but destroy sites sacred to Native Americans.
The US Forest Service published an environmental impact statement for the Resolution Copper project that allows the federal government to swap land containing a large copper deposit for nearby acreage that Rio owns.
The miner is eager to boost copper production to meet burgeoning demand from electric vehicles (EVs) manufacturers and other emerging green technologies. EVs use twice as much copper as internal combustion engines.
The publication was opposed by environmentalists who fear the mine could pollute local water supplies and Native Americans who consider the land home to religious deities.
The government must execute the land swap within 60 days of the environmental statement's publication, a stipulation laid out in a 2014 law signed by then-President Barack Obama.
The mine could supply a quarter of US copper demand if developed and generate more than $280-million in annual taxes, the Forest Service said on Friday.
"We have to balance demand for mineral extraction and the related economic benefits with our commitment to environmental stewardship and sustainability," said the Forest Service's Tom Torres. "This project is complex and the impacts were rigorously analyzed."
Rio still needs federal construction permits, a process that could take years. The company has also promised to seek tribal consent for the mine. It was not immediately clear what will happen to the land should Rio obtain it but decide not to build the mine.
"This is a starting point from which we are committed to continue building constructive relationships through ongoing dialogue with Native American tribes," Arnaud Soirat, who runs Rio's copper and diamond division, said on Friday.
BHP Group, which is developing the project with Rio, said it recognises the land "has historical cultural significance for Native American tribes" and plans to monitor Resolution's tribal negotiations.
Arizona Governor Doug Ducey, a Republican, praised the decision, saying the state "can have a robust mining sector while protecting our environment and cultural history."
Some Native Americans work for and support the Resolution project, though many others have vowed to forcefully oppose it.
"I'll defend this land to the very end," said Wendsler Nosie, the former chairman of Arizona's San Carlos Apache tribe who has formed a protest camp at the mine site. "It's silly for anyone to think" the companies could offer anything to gain tribal consent.
Wendsler and other San Carlos Apache tribe on Tuesday sued to block publication of the environmental study.
On Thursday, a judge declined to issue a restraining order to block publication, though he hinted the land swap was not a foregone conclusion and set several court hearings for coming weeks.
Tribal representatives said they were not surprised the environmental study was published and look forward to the hearings.
"Everything will get sorted out," said Michael Nixon, a lawyer for the tribal members opposed to the mine.
Tribal members have also filed a property lien that essentially asks a court to find that the US government has illegally occupied the land for more than 160 years and has no right to give it to anyone.
The disputed land swap comes just months after Rio bowed to harsh investor criticism and social pressure for destroying indigenous sites in Australia, a mistake that Native Americans say the mining giant is poised to repeat in Arizona.