In a long-anticipated but highly controversial move, the Trump administration has officially renewed two federal mineral leases for the proposed Twin Metals copper-nickel mine on the edge of the Boundary Waters in northeastern Minnesota.

It's a significant step in the state's yearslong battle over opening up Minnesota to copper mining, and it clears the way for Twin Metals to become the second such mine seeking state regulatory approval.

In announcing the decision Wednesday, the U.S. Department of the Interior said mineral mining benefits national security and the economy.

"Mining on public lands balances conservation … with the need to produce minerals that add value to the lives of all Americans by providing raw materials used in the manufacture of medical aids, automobiles, smartphones and computers, and household appliances," said Joe Balash, Interior's assistant secretary for land and minerals management.

U.S. Rep. Pete Stauber, a Republican from Duluth, commended the renewals and brushed aside concerns raised by state and national conservation groups.

"In northeastern Minnesota, mining is our past, present, and our future," Stauber said in a statement. "We know that with modern technology, we can develop the resources that all Americans utilize and create a boon for Minnesota, while preserving our precious environment."

At issue is the underground copper-nickel mine that Twin Metals Minnesota, a St. Paul-based subsidiary of Chilean mining company Antofagasta, wants to build about 9 miles southeast of Ely, in the Superior National Forest.

The Obama administration terminated Twin Metals' federal mineral leases in 2016, arguing that the lease language did not require them to be renewed and that hard-rock metal mining posed too many environmental risks so close to the Boundary Waters Canoe Area Wilderness (BWCA), the nation's most visited protected wilderness. After robust lobbying by Antofagasta, Trump's Interior Department reversed course last year.

The about-face is being litigated in federal court in the District of Columbia, but there are no stays associated with the action. The lease renewals open the door for Twin Metals to start its formal permitting process with the state.

Twin Metals issued a statement calling the lease renewals "a critical step" in moving the project forward.

"It's very good news for us and for the communities in northeastern Minnesota who look forward to the hundreds of jobs and major economic development this mine will bring," said Twin Metals Minnesota CEO Kelly Osborne.

The St. Paul-based company said it has spent $450 million developing the mine and that it will submit its mine proposal to state and federal agencies "in coming months." That step will start environmental reviews.

The lease renewals triggered a cascade of denunciations from conservation groups and other mine opponents.

"Is no place sacred?" asked National Wildlife Federation President and CEO Collin O'Mara in a statement.

"This abominable decision to reissue expired permits to sulfide-ore copper mining in a place so pristine you cannot use a motorized boat shows the depths of the Department of the Interior's imbalance toward mining at all costs," O'Mara said.

Tom Landwehr, the former Department of Natural Resources commissioner who now heads the Campaign to Save the Boundary Waters, accused federal regulators of "ignoring science and legal process."

"I'm outraged at the way that the Trump administration is treating the Boundary Waters and the wilderness," Landwehr said in an interview.

Landwehr said the Twin Metals leases were lawfully terminated in 2016, and that Twin Metals "doesn't have clear title to those leases." Given the importance of the Boundary Waters and the high risk of environmental damage from a copper mine in the same watershed, the controversy "is right in the Top 10 of most important issues facing Minnesota," Landwehr said.

U.S. Rep. Betty McCollum, a Democrat from St. Paul and vigorous mine opponent, issued a strongly worded statement decrying the pollution track record of mineral mines and vowing to challenge Interior's decision.

"The rush to issue mineral leases to Twin Metals and allow them to pursue sulfide-ore mining within the watershed of the Boundary Waters Canoe Area (BWCA) is shortsighted and irresponsible," McCollum said. "As the most visited wilderness area in America, the BWCA is a unique, iconic, and irreplaceable national treasure that must be protected."

The Twin Metals copper-nickel mine is one of two hotly contested copper-nickel mines proposed for northeastern Minnesota, home to one of the world's largest untapped mineral reserves.

The mines would be the state's first hard-rock metal mines, a type of mining that carries far greater environmental risks than mining for taconite or iron ore because copper is extracted from sulfur-bearing ore that, when exposed to oxygen or water, generates toxic sulfuric acid — often called acid mine drainage — that can pollute nearby waters.

Most copper mining in the U.S. is done in arid regions, such as Arizona. A 2012 study by the environmental group Earthworks found that of 14 U.S. copper-sulfide mines reviewed, all had pipeline spills or other types of accidental releases. Nine of the 14 experienced tailings spills.

The other copper mine proposed for northeast Minnesota is much further along, having received all the required state permits. That project is being developed by PolyMet Mining Inc., a Hoyt Lakes affiliate of Swiss-based conglomerate Glencore. It wants to build an open-pit copper mine at an existing taconite site south of Babbitt. The project faces numerous legal challenges.