China announced an export ban on Tuesday, preventing the sale of certain rare earth minerals to the U.S., including gallium, germanium, and antimony — all materials that have key military and technological applications.

The decision serves as a prelude to what could become an escalating trade conflict as President-elect Donald Trump, who had a firmer policy toward China in his first term than President Joe Biden has had during his, returns to office.

The ban also includes exports of “super-hard” materials used in a variety of industrial processes.

Gallium and germanium are used in various components of advanced technology, including the production of semiconductors, which are used in both civilian and military computer technology and are essential for advanced artificial intelligence.

China dominates the production of both materials, producing 83 percent of the world’s germanium and 94 percent of the world’s gallium.

Antimony is essential for numerous military products and is used in night vision goggles, explosives, optics, armor-piercing ammunition, and even nuclear weapons.

The U.S. is extremely dependent on China for its supply of antimony, meaning that a ban on Chinese antimony exports could pose serious problems for the U.S. military’s supply of essential equipment.

The new ban came in response to a Monday decision to further restrict the export of advanced computer chips to China, adding more than 100 Chinese companies to a restricted trade list in an effort to impede China’s AI ambitions.

“I want to reiterate that China firmly opposes the U.S. overstretching the concept of national security, abuse of export control measures, and illegal unilateral sanctions and long-arm jurisdiction against Chinese companies,” said Chinese Foreign Ministry Spokesman Lin Jian.

“China has lodged stern protests with the U.S. for its update of the semiconductor export control measures, sanctions against Chinese companies, and malicious suppression of China’s technological progress,” he added.

China’s new restrictions came just days after President-elect Trump threatened China and other BRICS nations with 100 percent tariffs if they move forward with plans to abandon the U.S. dollar as the standard for international trade.