A leaked U.S. military assessment says the Chinese military may soon deploy a high-altitude spy drone that travels at least three times the speed of sound, the Washington Post reported late on Tuesday.

The newspaper cited a secret document from the National Geospatial-Intelligence Agency.

The document, which Reuters could not confirm or verify independently, features satellite imagery dated Aug 9 that shows two WZ-8 rocket-propelled reconnaissance drones at an air base in eastern China, about 350 miles (560km) inland from Shanghai, according to the newspaper.

The U.S. assessment said China's People's Liberation Army (PLA) had "almost certainly" established its first unmanned aerial vehicle unit at the base, which falls under the Eastern Theater Command, the branch of the Chinese military responsible for enforcing Chinese sovereignty claims over Taiwan, the newspaper reported.