The U.S. Department of Defense plans to continue working with rare earths companies to ensure diverse American supply of the critical minerals used across the economy, a defense official told Reuters on Tuesday.

MP Materials, the operator of the only rare earths mine in the United States, has signed a $500 million deal with Apple.

Apple Inc. has struck a $500 million deal to buy rare-earth minerals from MP Materials Corp., the US producer that just last week secured backing from the Pentagon.