Chinese President Xi Jinping recently visited a facility in the city of Ganzhou where rare earth minerals are mined.
That's fueled speculation that these materials might be used to retaliate against the U.S.
China's Xinhua News Agency reported on Monday. that President Xi was accompanied by Liu He, the vice premier who's been leading the Chinese side in the trade negotiations with Washington.
Ganzhou is known for its rare-earths mining and processing industry.
The U.S. relies on China, the dominant global supplier, for about 80-percent of its rare earths imports.