Washington, (PTI) In yet another swipe at China, President-elect Donald Trump today said the US should let the Communist giant keep the Navy's unmanned underwater drone after Beijing agreed to return in an "appropriate manner" the device it had seized in the disputed South China Sea.

"We should tell China that we don't want the drone they stole back - let them keep it!" Trump tweeted, hours after Pentagon announced it had reached an understanding with China for the return of the drone.

The Pentagon had alleged that the drone was unlawfully seized by China on December 15 in the SCS while it was being recovered by a US Navy oceanographic survey ship.

The US lodged a formal diplomatic complaint and demanded the drone back. The incident is among the most serious military confrontations between the two powers for decades.

China yesterday slammed the US for "making a fuss" over the seizure of its underwater drone and said it will return the device in an "appropriate manner".

Defence Ministry spokesperson Senior Colonel Yang Yujun dismissed the US allegations, insisting that China seized the underwater glider to ensure the safe navigation of passing ships.

Trump's latest tweet was the second time the President-elect blasted China for the seizure.

Earlier, he accused China of stealing American drone.

"China steals United States Navy research drone in international waters - rips it out of water and takes it to China in unpresidented (sic) act," Trump tweeted, misspelling unprecedented.

He later reissued the tweet, correcting the spelling.

Trump has repeatedly infuriated China in recent weeks, questioning decades-old US policy on Taiwan, making phone call to Taiwanese President Tsai Ing-wen and calling Beijing a currency manipulator.

The drone incident, the latest encounter in international waters in the South China Sea region, occurred earlier this week about 161 km off the Philippine port at Subic Bay.

The USNS Bowditch had stopped in the water to pick up two underwater drones. At that point, a Chinese naval ship that had been shadowing the Bowditch put a small boat into the water. That small boat came up alongside and the Chinese crew took one of the drones.

The US got no answer from the Chinese on the radio when it said the drone was American property, a US defense official was quoted as saying by the CNN.

As they turned away, the Chinese did come up on the radio and indicated they were returning to their own operations.

US oceanographic research vessels are often followed in the water under the assumption they are spying.

Although it is unclear what the motivation was for the Chinese action, the seizing of the drone comes on the heels of other provocative incidents that have happened since Trump received a congratulatory call from Taiwan's President, a violation of the US's agreement with China's "One China policy." China publicly voiced its disapproval of that incident and protested to the White House at the time.