President Donald Trump’s administration has added 28 Chinese organizations to a blacklist over their role in human rights abuses, blocking them from doing business with American companies.

The blacklist, so-called Entity List, identifies organizations reasonably believed to be involved, or to pose a significant risk of being or becoming involved, in activities contrary to the national security or foreign policy interests of the United States.

These entities have been implicated in human rights violations and abuses in the implementation of China’s campaign of repression, mass arbitrary detention, and high-technology surveillance against Uighurs, Kazakhs, and other minority groups in Xinjiang autonomous region.

Among these entities are eight Chinese technology giants, including Dahua Technology, Hikvision, IFLYTEK, Megvii Technology, Sense Time, Xiamen Meiya Pico Information, Yitu Technologies, and Yixin Science and Technology.

According to Bloomberg, Dahua and Hikvision are two of the world’s largest manufacturers of video surveillance products, accounting for a third of the global market for video surveillance. Sense Time, meanwhile, is the world’s most valuable artificial intelligence startup.

The organizations on the Entity List are now prohibited from buying American products unless they are granted a U.S. government license.

The blacklist was announced on the same day the U.S. and Chinese negotiators began their working-level preparations for high-level trade talks due to begin on Thursday, Oct. 10, in Washington.

The Trump administration has been imposing punitive tariffs on Chinese imports over accusations of its theft of intellectual property, forced transfer of technology, cyberhacking, and industrial espionage.