US President-elect Donald Trump says he will not commit to the "one-China" policy until he sees progress from Beijing in its currency and trade practices, in an interview with the Wall Street Journal.

Key points: Trump says all policies on China are "under negotiation"

Trump says all policies on China are "under negotiation" China urges Trump to recognise sensitivity of Taiwan issue

China urges Trump to recognise sensitivity of Taiwan issue Trump also says he may scrap sanctions against Russia

Mr Trump was asked by the Journal if he supported the "one-China" policy on Taiwan, which has underpinned US relations with Beijing for decades.

"Everything is under negotiation including one China," he replied.

The United States has acknowledged the Chinese position that there is only one China and that Taiwan is part of China.

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

Mr Trump angered the Chinese by taking a congratulatory phone call after his election win from Taiwan's leader and questioning the "one-China" policy.

China's Foreign Ministry responded by saying the "one-China" principle was non-negotiable and was the "political basis" for China-US relations.

"We urge the relevant parties in the United States to recognise the high degree of sensitivity of the Taiwan issue and abide by commitments made by successive US administrations from both parties to pursue the one-China policy … and properly handle the Taiwan issue so as not to affect the stable development of China-US relations and cooperation between the two countries," spokesman Lu Kang said.

'Certainly they are manipulators'

Mr Trump also made clear his displeasure with China's currency practices in the hour-long interview.

"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 told the Journal.

"Our companies can't compete with them now because our currency is strong and it's killing us."

In the past, Mr Trump has said he would label China a currency manipulator after he takes office.

But the President-elect told the Journal he would not take that step on his first day in the White House.

"I would talk to them first," he said.

"Certainly they are manipulators … but I'm not looking to do that," he said.

Trump may scrap sanctions against Russia

Donald Trump says he wants to meet with Vladimir Putin once he takes office. ( Reuters: Carlo Allegri/Mikhail Klimentyev )

Mr Trump also discussed US-Russia relations and suggested he might do away with the sanctions imposed by the Obama administration in late December in response to Moscow's alleged cyber attacks, but only if Moscow proved helpful in battling terrorists and reaching other goals important to Washington.

He said: "If you get along and if Russia is really helping us, why would anybody have sanctions if somebody's doing some really great things?"

Mr Trump told the newspaper he was prepared to meet with Russian President Vladimir Putin some time after he is sworn in on January 20.

"I understand that they would like to meet, and that's absolutely fine with me," he said.

Reuters