But Pentagon said the $150,000 glider is 'clearly marked' as belonging to the US

China claims it did not know the drone belonged to the US when it removed it

China has accused the US of 'hyping up' its seizure of a US Navy drone just hours after Donald Trump ramped up his rhetoric against the country.

Trump took to Twitter on early Saturday morning to lash out at China for seizing the unmanned drone two days ago in the South China Sea.

'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 wrote in a misspelled tweet.

Trump deleted his original tweet, posted at 4.30am, after he was ridiculed online and later issued the same message with the correct spelling.

His inflammatory message came just hours after a Chinese official said the country was in talks with the American military for a 'smooth resolution' over the drone.

Donald Trump has accused China of stealing a US Navy drone, just hours after a Chinese official said the country was in talks with the US military for a 'smooth resolution'

Trump fired off his criticism nearly two days after the Chinese Navy seized an unmanned underwater glider right in the South China Sea on December 15

But China's Defense Ministry has since changed their tone, hitting back with a biting response as it revealed the drone would be returned.

'China decided to return it to the US side in an appropriate manner, and China and the US have all along been in communication about it,' the statement read.

'During this process, the US side's unilateral and open hyping up is inappropriate and is not beneficial to the smooth resolution of this issue,' it added.

'We express regret at this.'

The US said late Saturday that it had 'secured an understanding' through 'direct engagement with Chinese authorities' that the drone would be returned.

The capture - the first of its kind in recent memory - took place on December 15 just as the USNS Bowditch, an American oceanographic survey ship, was about to retrieve the unmanned underwater glider.

When the Bowditch stopped to collect the underwater equipment, a Chinese warship that had been following it dropped a boat into the water the pulled up alongside the US vessel and snatched the drone, according to CNN.

The USS Bowditch had been sampling and data collection of surface, midwater and ocean floor measurements, and US officials received no reply from the Chinese when they radioed to state the drone was American.

Trump's comments come just weeks after he potentially thrust US relations with China in chaos after calling Taiwan's president and criticizing China's government

The US crew had hoped to start communications with the Chinese vessel to get the drone back, but the ship eventually responded to say it was returning to normal operations and left the area, according to NBC News.

The Department of Defense released a statement, saying it was: 'not the sort of conduct we expect from professional navies.'

US officials issued a formal diplomatic complaint over the seizure and demanded the return of the $150,000 drone, which was collecting unclassified scientific data.

'It is ours. It's clearly marked as ours,' Navy Capt Jeff Davis said on Friday.

'We would like it back, and we would like this not to happen again.'

Meanwhile, China's Defense Ministry claimed that a Chinese navy lifeboat had discovered what first appeared to be a peace of 'unidentified equipment'.

Defense Ministry spokesman Yang Yujun said the vessel removed the item 'in order to prevent this device from posing a danger to the navigation of passing ships and personnel'.

'The Chinese lifeboat adopted a professional and responsible attitude in investigating and verifying the device,' he added.

It was only then, Yajun claimed, that the Chinese navy realized it was a US drone.

A Chinese Navy warship has seized an underwater drone deployed by an American oceanographic vessel in international waters in the South China Sea. Pictured is a Chinese ship in the Bohai Sea

The incident took place on December 15 northwest of Subic Bay just as the USNS Bowditch (pictured), an oceanographic survey ship, was about to retrieve the unmanned vehicle

The statement also accused the US of deploying ships to conduct 'renaissance and military surveying' in China's presence.

'China is resolutely opposed to this and requests the US stop such activities,' Yajun said.

The United States has maintained that the drone was operating lawfully while conducting a 'military survey' in the South China Sea.

'It's a sovereign immune vessel,' a US official said of the drone, adding that it was 'clearly marked in English not to be removed from the water - that it was US property'.

Arizona Sen John McCain, who is the chairman of the Senate Armed Services Committee, called the seizure a 'flagrant violation of the freedom of the seas'.

'China had no right to seize this vehicle. And the United States must not stand for such outrageous conduct,' he wrote in a statement released on Saturday.

'This brazen provocation fits a pattern of increasingly destabilizing Chinese behavior, including bullying its neighbors and militarizing the South China Sea.'

'Freedom of the seas and the principles of the rules-based order are not self-enforcing. American leadership is required in their defense. But that leadership has been sorely lacking,' he added, hitting out at Obama.

Before the defense ministry issued its statement, China said on Saturday that it was in contact with its American counterparts on 'appropriately handling' the seizure, one of the most serious incidents between the two militaries in years.

'According to (our) understanding, the US and Chinese sides are working on appropriately handling this matter through channels between the two militaries,' the foreign ministry said in a statement.

The drone conflict now seems to be resolved, but critics are still poking fun at Trump's most recent spelling mistake.

Even Merriam-Webster, a publishing company known for its dictionaries, joined in by linking a definition to the word 'Huh'.

'Good morning! The #WordOfTheDay is...not 'unpresidented'. We don't enter that word. That's a new one,' the tweet read.

Trump deleted the original tweet and rewrote it with the correct spelling of 'unprecedented', but the ridicule continued.

Trump deleted the original tweet and rewrote it with the correct spelling of 'unprecedented'

Critics took an easy shot at the president-elect's spelling mistake, and the Merriam-Webster Twitter account joined in with the mockery

SPELLING ERRORS IN TRUMP'S TWEETS December 15, 2016: 'If Russia, or some other entity, was hacking, why did the White House waite so long to act?' December 10, 2016: 'Reports by @CNN that I will be working on The Apprentice during my Presidency, even part time, are rediculous & untrue – FAKE NEWS!' July 29, 2016: 'Hillary Clinton should not be given national security briefings in that she is a lose cannon with extraordinarily bad judgement & insticts.' July 24, 2016: 'Looks to me like the Bernie people will fight. If not, there blood, sweat, and tears was a total waist of time. Kaine stands for opposite!' March 18, 2016: 'Heading to Phoneix. Will be arriving soon. Tomorrow a big day. Tremendous crowds expected!' March 6, 2016: 'All of the phony T.V. commercials against me are bought and payed for by SPECIAL INTEREST GROUPS, the bandits that tell your pols what to do' February 26, 2016: 'Lying Ted Cruz and leightweight chocker Marco Rubio teamed up last night in a last ditch effort to stop our great movement. They failed!' February 26, 2016: 'Leightweight chocker Marco Rubio looks like a little boy on stage. Not presidential material.' February 26, 2016: 'Wow, every poll said I won the debate last night. Great honer!' January 31, 2016: 'Ted Cruz is totally unelectable, if he even gets to run (born in Canada). Will loose big to Hillary. Polls show I beat Hillary easily! WIN!' January 19, 2016: 'Wow, the highly respected Governor of Iowa just stated that 'Ted Cruz must be defeated.' Big shoker! People do not like Ted.' June 25, 2015: 'I hear that dopey political pundit Lawrence O'Donnel, one of the dummer people on television, is about to lose his show- no ratings? Too bad' Advertisement

The president-elect's inflammatory tweet comes just weeks after he potentially thrust US relations with China in chaos after calling Taiwan's president and criticizing China's government.

Chinese admiral Yang Yi said he was unsure of the reasoning behind seizing the drone, but said Trump's recent comments had hurt the relationship between the two nations.

'It's natural for us to take possession of and research for a bit these types of things that America sends to our doorstep,' Yang told the Global Times.

'The louder they shout, the more their protests ring hollow.'

China's media outlets have speculated whether Trump's protocol-shattering call with Tsai Ing-wen and his subsequent Twitter tirade against Beijing's policies could upend the delicate balance between the world's two largest economies.

'Provoking friction and messing up China-US relations won't help 'make America great again',' a front-page opinion piece in China's People's Daily said. The newspaper is a mouthpiece for the country's Communist Party.

The nationalist Global Times newspaper's Chinese edition also ran a page-one story on Trump's 'inability to keep his mouth shut', damning his 'provocation and falsehoods'.

Trump fired off two tweets on Sunday blasting China for devaluing its currency, taxing American imports, and building military installations in the South China Sea.