China has strongly rejected US President-elect Donald Trump’s contention that the “One China” policy on Taiwan is negotiable, warning that it was the “political foundation” which underpinned the relationship between the US and China.

The rising tensions over Taiwan came as Chinese state media took aim at incoming US Secretary of State Rex Tillerson, reminding him China was “a big nuclear power” after he suggested a more aggressive strategy towards Beijing in the contested waters of the South China Sea.

In an interview with the Wall Street Journal, Mr Trump said he would not commit to the “One China” policy, which holds that Taiwan belongs to Chinese, until he saw progress from Beijing in its currency and trade practices.

“Everything is under negotiation including ‘One China’,” Mr Trump said, prompting China’s Foreign Ministry spokesman Lu Kang to urge the US to “properly handle the Taiwan issue”.

“The ‘One China’ principle is the political foundation of Sino-US relations and it is non-negotiable,” Mr Lu said.

“We urge the relevant parties in the US to recognise the high sensitivity of the Taiwan issue and abide by the pledges by successive US administrations from both parties.”

As China gets ready to welcome the Year of the Rooster, this factory is busy making Trump-inspired inflatable roosters. pic.twitter.com/cPDfLXZBhv

— AJ+ (@ajplus) January 13, 2017

China regards Taiwan as a renegade province and, since 1979, the US has acknowledged Beijing’s claim that Taiwan is part of China under a set of protocols known as the “One China” policy.

“There is only one China in the world. Taiwan is an inseparable part of Chinese territory and the People’s Republic of China is the sole legitimate government representing China,” Mr Lu said.

“These are facts recognised by the international community and no one can change this.”

Some Chinese analysts believe Mr Trump is using Taiwanese sovereignty as a bargaining chip for trade issues.

Mr Trump has previously angered Beijing by taking a congratulatory phone call from Taiwan’s leader, Tsai Ing-wen, after his election win.

During the hour-long interview with the Journal, Mr Trump also spoke bluntly about his displeasure with China’s currency practices.

“Instead of saying, ‘we’re devaluating our currency’, they say, ‘oh, our currency is dropping’. It’s not dropping. They’re doing it on purpose,” he said.

Donald Trump has softened his promise to label China a currency manipulator on his first day in office.

“Our companies can’t compete with them now because our currency is strong and it’s killing us.”

While campaigning for the presidency, Mr Trump said he would label China a currency manipulator after taking office. However he told the Journal he would not take that step on his first day in the White House, which is next Friday.

“I would talk to them first,” Mr Trump said.

“Certainly they are manipulators … but I’m not looking to do that,” he said.

Meanwhile, Mr Tillerson did little to defuse the US-China tensions at his confirmation hearing during the week, suggesting China should be denied access to islands it has built up in the South China Sea.

The Chinese media has urged Rex Tillerson to polish his diplomacy skills

The Global Times, a provocative but state-sanctioned Chinese newspaper, countered that “unless Washington plans to wage a large-scale war in the South China Sea, any other approaches to prevent Chinese access to the islands will be foolish”.

“Tillerson had better bone up on nuclear power strategies if he wants to force a big nuclear power to withdraw from its own territories,” the unbylined opinion piece suggested.

“If Trump’s diplomatic team shapes future Sino-US ties as it is doing now, the two sides had better prepare for a military clash.”

-with agencies