By Timothy Gardner

WASHINGTON, March 9 (Reuters) - The U.S. mining industry asked the U.S. Supreme Court on Friday to overturn an Obama-era rule that prohibits the mining of uranium on public lands adjacent to the Grand Canyon National Park.

The National Mining Association (NMA) and the American Exploration and Mining Association (AEMA) filed petitions asking the court to reverse the Obama administration's 2012 ban on new uranium mining claims on more than 1 million acres of public land adjacent to the canyon.

In 2012, Ken Salazar, then the secretary of the interior, instituted the ban for 20 years on the public lands that the Havasupai tribe relies on for water. The ban was upheld by the U.S. 9th Circuit Court of Appeals in December.

NMA spokesman Luke Popovich said his organization was challenging Salazar's constitutional authority to declare the large land withdrawal, and he said uranium mining does not harm the land.

"There is scant evidence that uranium mining outside the park boundaries poses any threat to either the environment or visitor experience," Popovich said. He said Salazar ignored a finding by the Interior Department's Bureau of Land Management that showed mining would have little impact.

Conservation groups disagreed and said the ban should remain in place until scientists have time to study the contamination risks. "Is it worth gambling the future of the Grand Canyon to allow private companies to line their pockets when the risks to groundwater are unknown?" said Roger Clark, a program director at the Grand Canyon Trust.

Currently the global uranium market is so flooded that mining in the United States for the mineral used in nuclear power plants and nuclear weapons is not profitable. But that could change as the administration of President Donald Trump is considering protections on the mineral that could increase demand for domestically mined uranium.

Last month uranium miner Energy Fuels said it had won federal approvals to expand operations at two mines in southeastern Utah after years of challenges from conservation groups worried about emissions of radon gas.

Other companies have urged Interior Secretary Ryan Zinke to reverse the 2012 ban. Last May, Vane Minerals LLC, a company in Arizona, told Zinke in a letter the company would appreciate it if he could begin the process to "terminate" the ban. A copy of the letter was seen by Reuters.

Vane did not immediately respond to a request for comment about the letter. The Interior Department did not immediately respond to a request for comment about the letter or the petitions. (Reporting by Timothy Gardner; Editing by Cynthia Osterman)