The Pentagon is taking immediate action to boost critical mineral production in the U.S. and counter China's dominance of the supply chain for rare earth magnets, a defense official told CNBC on Tuesday.

The Defense Department last week agreed to buy a direct equity stake in MP Materials, which will make the U.S. government the miner's largest shareholder. MP operates the only rare earth mine in the U.S. located at Mountain Pass, California, and a magnet plant in Fort Worth, Texas.

When asked whether the Pentagon is considering similar investments in other U.S. mining companies, the defense official said it is looking at opportunities to strengthen domestic critical mineral production.

"Rebuilding the critical minerals and rare earth magnet sectors of the U.S. industrial base won't happen overnight, but DoD is taking immediate action to streamline processes and identify opportunities to strengthen critical minerals production," official said in a statement.

Rare earths are used in weapons such as the F-35 warplane, drones and submarines among other other military platforms. The U.S. was almost entirely dependent on foreign countries for rare earths in 2023, with China representing about 70% of imports, according to the U.S. Geological Survey.

MP Materials CEO James Litinsky told CNBC last week that he views the public-private partnership with the Defense Department as a model for other companies in industries that are important for national security but struggle to compete against the state-backed enterprises in China.

"I'd like to think that this is sort of the first, it's a model," Litinsky told CNBC's "Squawk on the Street" on Thursday. "We have to deliver at MP and show that this is an incredible route to go. But it's a new way forward to accelerate free markets, to get the supply chain on shore that we want."

Interior Secretary Doug Burgum said in April that the U.S. government was looking at taking direct equity stakes in critical mineral and rare earth miners to break China's dominance. The Trump administration is also looking at stockpiling critical minerals and creating a sovereign risk insurance fund to protect companies investments' in federally approved projects, Burgum said at an energy conference in Oklahoma City.

The Pentagon makes long-term investments in mining, processing and refining critical minerals, the defense official told CNBC. It has invested $540 million so far to support a critical mineral and rare earth supply chain in the U.S. and allied nations, the official said.

"That is significant, and DoD will continue to such efforts in accordance with congressional appropriations and statutory authorities," the official said.

Correction: MP Materials operates a magnet plant in Fort Worth, Texas. An earlier version misspelled the name of the location.