President Donald Trump on Friday threatened China with a “massive” increase in tariffs and other economic countermeasures a day after the Chinese government announced new trade limits on crucial rare earth elements and related technologies.

China has become “very hostile” on trade matters, Trump said in a bombshell Truth Social post. “I was to meet President Xi in two weeks, at APEC, in South Korea, but now there seems to be no reason to do so.”

That meeting was seen by many as when the leaders of the world’s two largest economies would potentially announce a full-fledged trade deal.

A spokesperson for the Chinese Embassy in Washington, D.C., did not immediately respond to a request for comment on Trump’s post.

The president’s announcement immediately sent U.S. stocks to session low, with the S&P 500 falling nearly 1% after earlier trading in positive territory. The Nasdaq, which contains many tech companies that do business in China, slid about 1.2%.

On Thursday, China announced a series of new limits on the trade of rare earths and technologies related to them.

The regulations require foreign companies to get special approval to export items that contain even small traces of rare earths elements sourced from China. These critical minerals are needed in a broad range of products, from jet engines, radar systems and electric vehicles to consumer electronics including laptops and phones.

China and the U.S. have held more than three rounds of trade talks this year, with rare earths, TikTok and tariffs featuring in the discussions. After talks earlier this year in Geneva, the administration said China had decided to ease up on rare earth export controls.

But months later, the two sides met again in London, where they announced yet another agreement on the issue. The U.S. expected the issue to be “resolved” after those talks.

U.S. officials plan to meet with their Chinese counterparts for further talks in November, where rare earths will likely again take center stage.