By Dan Mangan

Copyright cnbc

President Donald Trump on Friday threatened to slap a “massive increase of Tariffs” on Chinese products imported into the United States to “financially counter” new export controls that China imposed on rare earths from that country.

Trump also threatened in a social media post to cancel his upcoming meeting with Chinese President Xi Jinping because of the dispute.

Stock markets dropped after Trump’s bellicose Truth Social post about China, in which he said that “there is no way that” country “should be allowed to hold the World ‘captive'” with its rare earth policy.

China controls about 70% of the global supply of rare earths minerals, which are critical for high-tech industries, including automobiles, defense and semiconductors.

“One of the Policies that we are calculating at this moment is a massive increase of Tariffs on Chinese products coming into the United States of America,” Trump wrote. “There are many other countermeasures that are, likewise, under serious consideration. Thank you for your attention to this matter!”

China’s Ministry of Commerce on Thursday said that foreign entities must now obtain a license to export products that contain more than 0.1% of rare earth sourced from that country, or that are manufactured using Chinese extraction, refining, magnet-making or recycling technology.

The new rules in rare earths exports are set to take effect on Dec. 1.