As the trade war continues to escalate, China has hit back at Trump by suspending exports of rare earth minerals.

China has tremendous power over the rare earths market. The country has the biggest mines, producing 270,000 metric tons (297,624 tons) of minerals last year compared to the 45,000 tons (40,823 metric tons) mined in the U.S. China supplies nearly 90% of the world’s rare earths because it also is home to most of the processing capacity.

China has managed to hit the U.S. where it hurts the most in response to the Trump administration’s tariffs, with restrictions on global exports of certain rare-earth elements that the U.S. has little ability to produce or refine.