The Pentagon on Friday demanded the return of a U.S. Navy underwater drone that was seized by a Chinese military vessel in the South China Sea, an incident that also triggered a formal diplomatic complaint from the U.S government.
U.S. officials say the seized device was collecting data on water salinity, surveying the ocean bottom and gathering other scientific information.
The U.S. State Department issued a formal demarche with Beijing about the incident, involving the unarmed torpedo-like vehicle known as an autonomous underwater glider.
Peter Cook, a Pentagon spokesman, said the Defense Department has “called upon China to immediately return an unmanned underwater vehicle that China unlawfully seized.”
Beijing should “comply with all of its obligations under international law” and recognize the device as “a sovereign immune vessel,” he said.
The incident began as the Bowditch, a U.S. survey vessel, attempted to retrieve two drones that the Navy said were collecting oceanographic information about 50 miles northwest of Subic Bay in the Philippines, once home to a major U.S. Navy base.
The crew had recovered one drone when a Chinese warship swept in and deployed a smaller boat that seized the second device, which was about 500 yards away, according to U.S. officials.
The Pentagon said the Bowditch contacted the Chinese ship on the radio to seek return of the drone, but the request was ignored.
The Navy said the incident occurred in international waters, and not in one of the areas claimed by China or other nations in the region’s numerous territorial and maritime disputes. It’s unclear where the drone had conducted its surveys, however, and whether China viewed it as a spy drone.
The seizure came at a tenuous time in U.S.-China relations.
China issued a strong condemnation of President-elect Donald Trump this week after he hinted his administration might be open to reevaluating four decades of U.S. policy toward China and Taiwan, which China regards as a rogue province.
The U.S. does not recognize Taiwan as an independent nation, but Trump earlier this month accepted a telephone call from Taiwan leader Tsai Ing-wen, setting off alarm bells in Beijing.
China’s Foreign Ministry warned that any changes in the so-called One China policy could rupture diplomatic ties. Chinese state media said Trump is “as ignorant as a child.”
Adding to tensions are recent commercial satellite imagery that analysts said showed China had installed antiaircraft guns and other weaponry on several of the artificial islands China is building off the mainland’s southern coast.
Submarine drones, outfitted with radar and sensors, are useful in a variety of roles in science and national security.
Unlike aerial drones, which are remotely controlled using GPS signals and data links, underwater craft are not able to receive satellite commands as they scour the ocean floor, sometimes for months at a time.
So the machines need to be able to navigate on their own to carry out missions.
The small unmanned subs can withstand the crushing pressures of the deep ocean, and have been used in ocean exploration and to locate airplane wreckage and shipwrecks.