But China has barely started setting up a system for issuing the licences. That has caused consternation among industry executives that the process could drag on and that current supplies of minerals and products outside of China could run low.

If factories in Detroit and elsewhere run out of powerful rare earth magnets, that could prevent them from assembling cars and other products with electric motors that require these magnets. Companies vary widely in the size of their emergency stockpiles for such contingencies, so the timing of production disruptions is hard to predict.

The so-called heavy rare earth metals covered by the export suspension are used in magnets essential for many kinds of electric motors. These motors are crucial components of electric cars, drones, robots, missiles and spacecraft. Gasoline-powered cars also use electric motors with rare earth magnets for critical tasks like steering.

The metals also go into the chemicals for manufacturing jet engines, lasers, car headlights and certain spark plugs. And these rare metals are vital ingredients in capacitors, which are electrical components of the computer chips that power artificial intelligence servers and smartphones.

Michael Silver, the chairman and chief executive of American Elements, a chemicals supplier based in Los Angeles, said his company had been told it would take 45 days before export licences could be issued and exports of rare earth metals and magnets would resume.

Silver said his company had increased its inventory last winter in anticipation of a trade war between the United States and China, and could meet its existing contracts while waiting for the licences.

Daniel Pickard, the chairman of the critical minerals advisory committee for the Office of the United States Trade Representative and Department of Commerce, expressed concern about the availability of rare earths.

“Does the export control or ban potentially have severe effects in the US? Yes,” he said.

Pickard, leader of the international trade and national security practice at the Buchanan Ingersoll & Rooney law firm, said a swift resolution of the rare earths issue was necessary because a sustained disruption of exports could hurt China’s reputation as a reliable supplier.

In a potential complication, China’s Ministry of Commerce, which issued the new export restrictions jointly with the General Administration of Customs, has barred Chinese companies from having any dealings with an ever-lengthening list of American companies, particularly military contractors.

One American mining leader, James Litinsky, the executive chairman and chief executive of MP Materials, said that rare earth supplies for military contractors were of particular concern.

“Drones and robotics are widely considered the future of warfare, and based on everything we are seeing, the critical inputs for our future supply chain are shut down,” he said.

MP Materials owns the sole rare earths mine in the United States, the Mountain Pass mine in the California desert near the Nevada border, and hopes to start commercial production of magnets in Texas at the end of the year for General Motors and other manufacturers.

A few Japanese companies keep rare earth inventories of more than a year’s supply, having been hurt in 2010 when China imposed a seven-week embargo on rare earth exports to Japan during a territorial dispute.

But many American companies keep little or no inventory because they do not want to tie up cash in stockpiles of costly materials. One of the metals subject to the new controls, dysprosium oxide, trades for $204 per kilogram in Shanghai, and much more outside China.

Rare earth magnets make up a tiny share of China’s overall exports to the United States and elsewhere. So halting shipments causes minimal economic pain in China while holding the potential for big effects in the United States and elsewhere.

Chinese customs officials are blocking exports of heavy rare earth metals and magnets not just to the United States but to any country, including Japan and Germany. Enforcement of the new export licence requirement, though, has been uneven so far among different Chinese ports, rare earth industry executives said.

Most but not all rare earth magnets include heavy rare earths, which are needed to prevent magnets from losing their magnetism at high temperatures or in some electrical fields. Some rare earth magnets are made only from light rare earths, and are not subject to export restrictions. Customs officials at a few Chinese ports are tolerating exports of magnets if they have only tiny traces of heavy rare earth metals in them, and if the magnets are not going to the United States.

Officials at other Chinese ports are taking a more stringent stance, however, demanding that exporters run tests to prove that any batch of magnets does not have heavy rare earth metals in them before the magnets can be loaded on a ship for export.

The Chinese export restrictions began taking effect before the Trump administration announced on Friday night that it would exempt many kinds of consumer electronics from China from its latest tariffs. Magnet exports continue to be blocked this weekend, five rare earth industry executives said.

Like most goods from China, the magnets are also subject to President Trump’s latest tariffs when they arrive at American ports.

Until 2023, China produced 99% of the world’s supply of heavy rare earth metals, with a trickle of production coming out of a refinery in Vietnam. But that refinery has been closed for the past year because of a tax dispute, leaving China with a monopoly.

China also produces 90% of the world’s nearly 200,000 tons a year of rare earth magnets, which are far more powerful than conventional iron magnets. Japan produces most of the rest and Germany produces a tiny quantity as well, but they depend on China for the raw materials.

China’s Ministry of Commerce did not reply to a request for comment.

The world’s richest deposits of heavy rare earths lie in a small, forested valley on the outskirts of Longnan in the red clay hills of Jiangxi Province in south-central China. And most of China’s refineries and magnet factories are in or near Longnan and Ganzhou, a town about 80 miles away. Mines in the valley ship ore to refineries in Longnan, which remove contaminants and sends the rare earths to magnet factories in Ganzhou.

China’s most famous factory for these magnets is operated by the JL Mag Rare-Earth Company, whose headquarters are in Ganzhou.

The factory supplies the world’s top two electric car producers, Tesla and China’s BYD, with the magnets that power their cars, rare earth industry executives said. BYD has said that it buys some of the world’s latest, most powerful magnets from JL Mag, with 15 times the magnetic force per cubic inch of volume as a conventional iron magnet.

Xi Jinping, China’s top leader, made a special inspection visit to JL Mag’s factory in Ganzhou in 2019, during heightened trade tensions in Trump’s first term. The trip was interpreted as a hint that China was ready to use its control over the materials to disrupt American supply chains, a step it did not take then but is doing now.

China paused the mining of heavy rare earths near Longnan a few years ago because it was causing severe chemical pollution.

On Friday, at the site of one mine near Longnan, a diesel generator was humming and liquids were gurgling through plastic pipes, indicating that at least some mining operations had probably resumed. Heavy rare earths are mined by dumping strong chemicals into holes dug in the top of a hillside. The chemicals dissolve the ore and dribble out of the base of the hill, where they can be pumped to nearby pits for initial processing.

Written by: Keith Bradsher. Li You contributed research.

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