President Xi Jinping's country warns US over islands
Fears are growing Mr Trump will challenge China over the Spratly Islands.
At a press conference in Beijing on Tuesday, the foreign ministry spokesperson, Hua Chunying, urged the White House to “speak and act cautiously”.
Mr Hua was responding to comments made by White House press secretary, Sean Spicer, the previous day.
Mr Spicer told reporters the US would “make sure that we protect our interests” in the resource-rich trade route, through which $4.5tn (£3.4tn) in trade passes each year.
World leaders will undoubtedly be watching the tense talks unfold just days after Mr Trump’s inauguration.
The controversial billionaire businessman – now leader of the free world – has made little of who he will form allegiances with.
President Trump has been warned to back-off over South China Sea
The Subi Reef in the South China Sea, a part of the Spratly Islands group
But upsetting Beijing within days of taking office is little surprise.
Mr Trump’s nominee for secretary of state Rex Tillerson likened the artificial island building campaign in the South China Sea to “Russia’s taking of Crimea” less than a fortnight ago.
China hit back saying a “large scale war” in protecting its interests could not be ruled out.
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Undeterred by the Chinese response Mr Spicer continued with the dismissal of China’s perceived right over the islands.
He said: “It’s a question of if those islands are in fact in international waters and not part of China proper, then yeah, we’re going to make sure that we defend international territories from being taken over by one country.”
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Mr Spicer said he was not clear on what action could be taken by the US.
He said: “I think, as we develop further, we’ll have more information on it.”
Mr Trump may ramp up US troops in the South China Sea after meeting with his advisors.
Daniel Blumenthal, director of Asian Studies at the American Enterprise Institute, a conservative Washington-based thinktank, told the Guardian: “We’ve talked a big game on security but haven’t really followed it up all that well with the military muscle that was needed.”
Blumenthal said a “strong, persistent US naval presence” was required to back up a foreign policy “that at its bottom line says that China’s not going to control the South China Sea … But you can’t do that without military resources.”
China has previously been accused of militarising the islands – claims which it denies.
The Gaven Reefs are located in the Tizard Bank of the Spratly Islands in the South China Sea
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However, the country continues to insist upon sovereignty over nearly the entire South China Sea and in recent years has stepped up a campaign to cement its control.
Brunei, Japan, Malaysia, the Philippines, Taiwan and Vietnam also have claims over the islands.
A judgment by an international tribunal in The Hague came down overwhelmingly in favour of claims by the Philippines in July 2016.