Citing concerns of national security, the United States has restricted the sale of certain technological products to Chinese groups involved in military-related supercomputing.

The U.S. Commerce Department has added Sugon, the Wuxi Jiangnan Institute of Computing Technology, Higon, Chengdu Haiguang Integrated Circuit and Chengdu Haiguang Microelectronics Technology to an “Entity List,” preventing them from purchasing certain U.S. products without government approval, according to Reuters.

The recent U.S action is “all about the race to exascale computing, which China has designated as a major priority,” Paul Triolo of Eurasia Group told The Associated Press.

Excale computing is when a supercomputer is capable of performing a quintillion calculations per second (that’s a billion billion). Trilo stresses the military applications of excale capable supercomputers, explaining how they will someday be used to run nuclear simulations, track missile trajectories and create algorithms to guide hypersonic missiles.

The U.S is invested in restricting China’s access to such technology and “is gradually squeezing off access to US technology for major elements of China’s next generation supercomputing,” Triolo told the AP.

This action by the U.S. Commerce Department takes places just days before a scheduled meeting between President Donald Trump and the Chinese head of state Xi Jinping to discuss ongoing trade negotiations, according to the Financial Times’s “Week Ahead” news report.

Given this, not everybody is happy about the timing of the new Entity List additions. “Chinese may see this as ill-timed bullying. They cannot be seen as making concessions to the United States, so this may have the effect of hurting any chances for trade agreement,” Amanda DeBusk, a partner at Dechert LLP and former Commerce Department assistant secretary for export enforcement, said to the AP.