US President-elect Donald Trump said the US does not necessarily have to stick to its long-standing position that Taiwan is part of "one China", questioning nearly four decades of policy, a move that Chinese experts described as "dangerous".

Trump's comments on Fox News Sunday came after he prompted sharp disagreement from China over his decision to accept a telephone call on Dec 2 from Taiwan leader Tsai Ing-wen.

China urged the United States to honor its commitment to the one-China policy, Foreign Ministry spokesperson Geng Shuang said on Dec 3. The one-China principle is the political foundation for the China-US relations, Geng said.

"I fully understand the ‘one China' policy, but I don't know why we have to be bound by a "one China" policy unless we make a deal with China having to do with other things, including trade," Trump told Fox News.

Chen Dongxiao, president of the Shanghai Institute for International Studies, said the one-China principle is vital to Sino-US relations; any attempt to shake it could cripple the bilateral relations.

"It's very dangerous for Trump to neglect such a cornerstone in the US-China relations and to try to link the one-China policy with other issues, such as trade," Chen said. "China should stand guard against any remarks and acts of the future Trump administration that challenge the one-China principle."

Zheng Changzhong, associate professor in international diplomacy at Fudan University in Shanghai, said he believed Trump's phone call with Tsai and his subsequent comments critical of China resulted from his businessman mentality and the fact that he was new to diplomacy.

"If he is making the comments with ulterior political intentions, it's maybe the time for people to be cautious of how the world order will be reshaped based on the interests of the United States," Zheng said.

Trump's call with Tsai was the first such contact with a Taiwan leader by a US president-elect or president since President Jimmy Carter switched diplomatic recognition to Chinese mainland from Taiwan in 1979.

Foreign Ministry had no immediate reaction to Trump's remarks.

After Trump's phone conversation with Tsai, the Obama administration reaffirmed the US' backing of the one-China policy on Dec 5.

White House Press Secretary Josh Earnest reiterated that the US is committed to the one-China policy, saying it's been in place for almost 40 years and has been geared to promoting peace and stability in the Taiwan Straits.

Following Trump's latest comments, a White House aide said the Obama administration had no reaction beyond its previously stated policy positions.

In the Fox interview, Trump criticized China over its currency policies, its activities in the South China Sea and its stance toward Democratic People's Republic of China. He said it was not up to Beijing to decide whether he should take a call from Taiwan's leader.

"I don't want China dictating to me, and this was a call put in to me," Trump said. "It was a very nice call. Short. And why should some other nation be able to say I can't take a call?

"I think it actually would've been very disrespectful, to be honest with you, not taking it," Trump added.

Former secretaries of state Madeleine Albright and Henry Kissinger both expressed their support for the one-China policy during an event hosted by the National Committee on US-China Relations in New York on Dec 5.

Some US analysts warned that Trump could provoke a military confrontation if he presses the Taiwan issue too far.

Mike Green, a former top adviser on Asia to former president George W. Bush, said in an interview with Reuters that ending the one-China policy would be a mistake because it would throw the US-China relationship into turmoil and jeopardize Beijing's cooperation on issues such as the Democratic People's Republic of Korea.

But Green, who is now with the Center of Strategic and International Studies, said he does not believe that Trump intends to go that far, and there was "logic to serving Beijing notice that he will not be dictated to on issues like Taiwan".

"China is more likely to let the whole relationship with the United States deteriorate in order to show its resolve on the Taiwan issue," Jessica Chen Weiss, an associate professor of government at Cornell University, told Reuters.

"When the decision to end a decades-long practice is made with so little warning and clear communication, it raises the likelihood of misunderstanding and miscalculation and sets the stage for a crisis between the United States and China over Taiwan," Chen Weiss said.

Trump nominated a long-standing friend of Beijing, Iowa Governor Terry Branstad, as the next US ambassador to China.

However, Trump is considering John Bolton, a former Bush administration official who has urged a tougher line on Beijing, for a senior role at the US State Department, according to a source familiar with the matter.

The source said Bolton was a leading candidate for the No. 2 job at the State Department.

Also on Sunday, some US senators signaled that Trump's leading choice for secretary of state, Exxon Mobil Corp chief Rex Tillerson, could have trouble winning confirmation because of his ties to Russian President Vladimir Putin.

Tillerson, 64, is the Texas-based oil company's CEO since 2006 and had moved ahead of other candidates for the position of the country's top diplomat.

Criticism from Republicans such as Florida Republican Marco Rubio and Senator John McCain as well as key Democrats suggest that nominating the Exxon chairman and CEO could become a distraction for the new president.

It also would become a proxy fight over Trump's position that Putin is an effective leader with whom he can reach agreements, a stance widely unpopular among lawmakers in both parties.

In what may be a message that he's still evaluating reaction to the choice, Trump said on Twitter on Sunday, "Whether I choose him or not for ‘State'- Rex Tillerson, the Chairman & CEO of ExxonMobil, is a world class player and dealmaker. Stay tuned!"

Xinhua contributed to this story.