WASHINGTON—The U.S. added 28 Chinese entities to an export blacklist Monday, citing their role in Beijing’s repression of Muslim minorities in northwest China, just days before high-level trade talks are set to resume in Washington.

The action, which the U.S. said wasn’t related to trade talks, was nonetheless likely to disturb Chinese officials already incensed over what Beijing sees as U.S. support for an increasingly disruptive pro-democracy movement in Hong Kong.

“I...