MP Materials, which runs the only American rare earths mine, announced a new $500 million agreement with tech giant Apple on Tuesday to produce more of the powerful magnets used in iPhones as well as other high-tech products like electric vehicles.

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.

The Pentagon has invested almost $540 million into critical minerals projects and "will continue such efforts in accordance with congressional appropriations and statutory authorities," the official said.