China is responsible for most of the world’s processing of rare earth metals and minerals, but its new export restrictions have raised the stakes for U.S. efforts to build its own supply chain and processing industry.

A US producer of rare earth metals stopped shipments to China after Beijing placed export controls on similar materials crucial for defense and technology manufacturing.

As the trade war worsens, Beijing has banned the export of critical minerals used in the defense industry — but also for some cancer treatments and MRI exams.