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.

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.

MP Materials has announced plans to expand rare earth mining and processing operations as Washington seeks to end its dependence on Chinese supplies.