The United States is posing a formal diplomatic protest to China after a Chinese Navy warship captured a U.S. drone in the South China Sea. The U.S. is protesting to have the unmanned, underwater drone (also called an unmanned underwater vehicle) returned, claiming that the drone was there legally, according to Reuters

A U.S. defense official confirmed to Reuters that the drone was seized on Thursday, northwest of Subic Bay near the Philipines. A U.S. oceanographic survey ship, the U.S. Naval Ship Bowditch was en route to pick up the drone when it was captured by the Chinese Navy. 

The defense official told Reuters that the drone was legally allowed to be in the South China Sea, saying that the unmanned drone "was lawfully conducting a military survey in the waters of the South China Sea." The official added that the drone is "a sovereign immune vessel, clearly marked in English not to be removed from the water, that it was U.S. property." Reuters reports the drone was picking up information about the water, such as clarity, salinity, and temperature. 

The U.S. has taken steps using diplomatic channels to get the drone back from China, and that China has received communications about the drone's return, but has not yet responded, according to Reuters.

Reuters further reports that China has anti-missile and aircraft weapons on all of the seven artificial islands they've built in the South China Sea, citing a recent report from a U.S.-based think tank. 

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