The Commerce Department on Friday took its broadest swipe yet at China’s supercomputing industry, imposing new export restrictions that effectively bar five major Chinese developers of next-generation, high-performance computing from obtaining U.S. technology.

Meanwhile, statistics reviewed by The Wall Street Journal show the Commerce Department has cut in half the number of licenses for U.S. tech companies to assign Chinese nationals to advanced engineering projects. The actions are the latest in a series of steps to keep advanced U.S. technology from China.

The Commerce Department’s supercomputer move could further strain relations between the U.S. and China ahead of a planned meeting in Japan next week between President Trump and Chinese President Xi Jinping aimed at breaking the impasse in the U.S.-China trade talks.

The Chinese supercomputer developers are at the heart of Beijing’s key technological objective of making the country’s first exascale computer, a next-generation machine that would be capable of doing one quintillion—or one billion billion—calculations a second.

Supercomputing is integral to the development of nuclear weapons, encryption, missile defense and other systems, and the U.S. and China are competing for dominance in the field. The U.S. now has the world’s two fastest supercomputers, followed by a Chinese-built computer in third place.