Ford CEO Jim Farley said that a rare earth minerals shortage is hurting production and caused the automaker to temporarily shut down one of its plants last month, according to an interview with Bloomberg TV.

Rare earth minerals, which are a set of 17 metallic elements, are integral to automobile production, and enable features like windshield wipers, seat belts and speakers to function. About 90% of the U.S.'s rare earth minerals come from China, the world's largest producer of rare earths, according to data from the Geological Survey.

China has leveraged its grip on rare earths and their widespread utility amid a trade war with the U.S. In April, Beijing announced greater export controls on the materials " a sticking point in tariff negotiations " along with other retaliatory trade measures. The controls require businesses to apply for a license to export rare earths, which U.S. automakers say they have been struggling to secure.