The deal would see the Defense Department take a 15% stake in MP Materials and spend billions of dollars investing in the company and purchasing its output.

The Defense Department is buying $400 million of stock in rare-earth mining company MP Materials as it seeks to boost domestic sources of the critical minerals.

July 7 (Reuters) - China's export restrictions on rare earths brought parts of the global auto supply chain to a halt and U.S. President Donald Trump to the negotiating table. But at home, they're a big headache for companies already struggling with a slow economy.