China's Ministry of Commerce did not immediately respond to a faxed request for comment. China's critical-mineral export controls have become a focus on Trump's criticism of Beijing, which he says has violated the truce reached last month to roll back tariffs and trade restrictions.
On Thursday, Trump and Chinese President Xi Jinping had a lengthy phone call to iron out trade differences. Trump said in social-media post that "there should no longer be any questions respecting the complexity of Rare Earth products." Both sides said teams will meet again soon.
U.S. auto companies are already feeling the impact of the restrictions. Ford shut down production of its Explorer SUV at its Chicago plant for a week in May because of a rare-earth shortage, the company said.