Is China testing submarine drones that could threaten US west coast or Panama Canal?

Underwater drones being tested by China could be used to blockade the Panama Canal or even the US west coast, an American defence publication has claimed.

The drones, referred to as XXLUUVs (Extra-Extra-Large Unmanned Underwater Vehicles), are highly classified and little is known for certain about them.

However, some clues have been gleaned from satellite imagery, eyewitness photographs and a builder’s concept model displayed at a defence exhibition, according to the Naval News website.

The report said the drones were believed to be by far the world’s largest and to be capable of sailing more than 10,000 nautical miles (18,500km) – about twice the width of the Pacific – allowing them to reach the western Americas, including the strategically vital canal.

Their internal weapons bays could carry sea mines or between eight and 12 torpedoes, “providing China with low-risk options to directly threaten West Coast ports”, the report published on Wednesday said.

Naval News earlier reported that two prototypes of a similar size but different design were spotted by satellites during tests in the South China Sea in September.

The drones were housed in specialised floating docks at two separate ports in Hainan province and were possibly competing for a contract with the Chinese navy.

Satellite images taken in January also showed that a tailless submarine, probably uncrewed, was being built in a shipyard in Guangzhou owned by the China State Shipbuilding Corporation (CSSC).

The drones are defined as “extra-extra-large” because they are estimated to be more than 40 metres (130 feet) long – close to the size of some smaller submarines and much more than any known extra-large drone.

XL drones include the US Navy’s Orca, which has a length of 26 metres, and two Chinese vessels – HSU100 and AJX002 – which are each around 20 metres.

The latter two models were on display during Beijing’s Victory Day parade in September and a Chinese military magazine has said they could carry out coordinated operations such as blockades and attacks.

The XXL models are presumed to be even more powerful, with information provided by the CSSC at last year’s Zhuhai air show in southern China giving some of the best clues about their performance.

The state-owned shipbuilder and warship developer displayed a model of what it called a “small special operations unmanned submarine”.

There is no proof that the vessel is the same as the ones being tested, but its appearance matches the sightings and the product specifications gave a length of 38 to 43 metres, which closely matches estimates made through observation.

CSSC said its drone could dive to a depth of between 300 and 450 metres and had a top speed of 20 knots (37km/h).