USNS Bowditch
The oceanographic survey ship, USNS Bowditch, which deployed an underwater drone was seized by a Chinese Navy warship in international waters in South China Sea on 15 December 2016 ~ file photo US Navy

China is expecting a "smooth" way to resolve an issue raised by the US navy after Beijing warship reportedly seized one of the US' underwater drones in the South China Sea, a state-run influential tabloid says.

The communist country referred to the US vessel as "unidentified equipment" that a Chinese naval vessel found in the disputed waterways. It was taken to be checked to prevent any navigational safety issues, the Global Times paper cited a Chinese military source as saying on Saturday (17 December).

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"This person said China has already received a claim request for the equipment from the US side, relevant parties from both sides have maintained smooth communication channels, and believe this issue will be smoothly resolved," the paper said.

"According to (our) understanding, the U.S. and Chinese sides are working on appropriately handling this matter through channels between the two militaries," The Associated Press quoted China's foreign ministry as saying on Saturday.

However, it did not give any details on what discussions were underway or why Beijing seized the US drone.

The incident had triggered the US to launch a formal diplomatic protest after the drone was seized on Thursday (15 December) and was thought to be the first in recent times where China has taken away American oceanographic vessel.

Pentagon press secretary Peter Cook called the seizure "unlawful" and urged China to return its unmanned underwater vehicle (UUV) "immediately, and to comply with all of its obligations under international law", CNN reported.

The drone was taken about 50 nautical miles northwest of Subic Bay off the Philippines just as the USNS Bowditch was about to reclaim it. The Pentagon confirmed the incident on Friday (16 December) and said the drone has no classified systems and is commercially available for about $150,000.

The UUV was part of an unclassified program to collect oceanographic data that is used to test water salinity, ocean temperature and clarity for a project to map underwater channels.

China is accused by its neighbours and the US of increasing its military presence in the South and East China Seas.

The incident also coincided with the rise in sabre-rattling from Chinese media and its military establishment over US President-elect Donald Trump's breach of diplomatic protocol and his criticism of Beijing's assertiveness and aggressive conduct in the mineral-rich waterways.

Meanwhile, a Chinese think tank, affiliated to the mainland government, said on Saturday (17 December) the incident only highlights how the militaries of the opponents have now entered a new phase of underwater competition.

"China wants to send out a signal that if you spy on us underwater and threaten our national security, we have measures to deal with it," South China Morning Post quoted Wu Shicun, president of the influential National Institute for South China Sea Studies, as saying. "On the South China Sea issue, we took in humiliations with a humble view in past years. I think this era has finished."