China's defense ministry did not immediately respond to a request for comment. The U.S. Department of Defense said it was "aware of the reports" but said it did not have additional comment beyond what was included in its annual report on the Chinese military this month.

The United States is years into its Next Generation Air Dominance (NGAD) program, which is developing a sixth-generation fighter aircraft, but it is not clear what form the effort will take under President-elect Donald Trump's incoming administration.

Europe and Asia are collaborating on a separate next-generation aircraft under the Global Combat Air Programme, and recently announced a joint British-Japanese company.