BEIJING—Cybersecurity proposals by China have U.S. businesses worried that the draft regulations represent additional barriers to the Chinese market, a concern that could complicate U.S.-China trade talks.

The new rules and standards, floated over the past two months with little fanfare, flesh out an existing cybersecurity law that Washington and many foreign businesses already consider draconian. Some would forbid certain data from leaving China or at least slow the process of dispatching data, which would increase uncertainties...