A U.S. official told top global semiconductor makers he wanted to revoke waivers they have used to access American technology in China, people familiar with the matter said, a move that could inflame trade tensions.

Currently, South Korea’s Samsung Electronics and SK Hynix as well as Taiwan Semiconductor Manufacturing enjoy blanket waivers that allow them to ship American chip-making equipment to their factories in China without applying for a separate license each time.

Jeffrey Kessler, head of the Commerce Department unit in charge of export controls, told the three companies this week he wanted to cancel those waivers, according to people familiar with the meetings. They said Kessler described the action as part of the Trump administration’s crackdown on critical U.S. technology going to China.

If carried out, the move could be disruptive both diplomatically and economically. Earlier this month, the U.S. and China agreed to a fragile trade truce in London. Part of the deal involved each country’s agreeing to hold off from introducing new export controls and other measures designed to hurt the other.

The action isn’t a new trade escalation but would be designed to make the licensing system for chip equipment similar to what China has in place for rare-earth materials, White House officials said. The U.S. and China continue to make progress on completing the agreement they reached in London and negotiating on trade, they said. 

“Chip makers will still be able to operate in China. The new enforcement mechanisms on chips mirror licensing requirements that apply to other semiconductor companies that export to China and ensure the United States has an equal and reciprocal process,” a Commerce Department spokesman said.

A new step making it harder for global chip makers to operate in China might still strike Beijing as a betrayal of the London deal. It could also strain the relationship between Washington and friendly governments in South Korea and Taiwan, whose companies would be most affected and have promised large investments in the U.S. in recent years. 

The Chinese factories in question—including a Samsung memory-chip factory in the Chinese city of Xi’an—are part of the global supply chain for memory, logic and other chips. While they generally don’t have the most advanced technology, the factories’ output is widely used in cars, consumer electronics and the like.

Industry officials said tighter curbs by Washington wouldn’t immediately force the factories to shut down, but over time, they could find it harder to operate effectively. That would disrupt global industry as companies are dealing with other issues triggered by the U.S.-China trade war, such as China’s limits on exports of rare-earth magnets.

The chip makers would likely seek case-by-case licenses from the U.S. government to supply their Chinese factories, while looking to replace U.S. equipment with alternatives from Japan and Europe. 

People involved in the discussions said revoking the waivers isn’t a done deal.

They said Kessler’s unit—the Commerce Department’s Bureau of Industry and Security—hasn’t secured buy-in from other parts of the U.S. government, such as the Defense Department. Opponents in the administration worry eliminating the waivers would ultimately end up boosting Chinese companies and give China control of the plants. 

Kessler and other national-security hawks have taken a hard line on cutting off China from American technologies, arguing that aggressive measures are needed to limit the country’s advances in critical sectors and spur development of supply chains outside China. Those efforts have put them in conflict with pro-business officials.

In recent weeks, the administration has halted sales to China of more high-end chips from Nvidia and Advanced Micro Devices. That has dented the U.S. companies’ revenue by billions of dollars. Commerce also weighed broad restrictions on sales of semiconductor manufacturing equipment to China, although a White House official said that move was no longer under consideration.