Chinese diplomacy has come far since the founding of the People’s Republic in 1949. But there is one cornerstone to its foreign policy that has stood unchanged – and been unnegotiable – ever since Mao Zedong (毛澤東). The one-China policy.

So when US President-elect Donald Trump indicated he was considering jettisoning his nation’s four-decade understanding with Beijing regarding the matter it inevitably sent shock waves across the Pacific.

And if Trump makes good on his words after coming to office, such “waves” will be more like a tsunami in the Taiwan Strait – one that has potential to sink relations between the world’s two most influential nations.

WATCH: Trump questions continuing one-China policy

“China is more likely to let the whole relationship with the United States deteriorate in order to show its resolve on the Taiwan issue,” said Jessica Chen Weiss, an expert on Chinese foreign policy at Cornell University.

Since his election last month, Trump has repeatedly challenged China’s most cherished principle. This month he became the first US leader to speak to Taiwan’s president since 1979 when he received a phone call from Tsai Ing-wen, enraging Beijing. He also pointedly referred to Tsai as the “president of Taiwan” – a break from previous protocol which refers to those holding the office as the island’s “leader”.

Last Sunday, in an interview with Fox News, he went even further, questioning why Washington should continue to observe the one-China policy unless Beijing was willing to make concessions on policies seen as obstructive to American interests. (He identified China’s exchange policy, tariffs and military buildup in the South China Sea, as well as North Korea’s nuclear programme).

While the White House moved to limit the damage – with spokesman Josh Earnest reconfirming US commitment to the policy – Trump’s remarks have nevertheless shocked the diplomatic world, raising fears over the impact on China-US relations and on global security.

One Chinese state-run newspaper warned of using force to take back Taiwan if Trump abandoned the policy, while Chinese Foreign Minister Wang Yi ( 王毅 ) described Trump’s act as “lifting a rock only to drop it on [his] feet”.

The stand-off adds to already chilly ties across the Taiwan Strait. These took on a distinct frostiness when Tsai, leader of the pro-independence Democratic Progressive Party, took office in May. The previous party in power on the island, the Kuomintang, or KMT, leans towards unification and has accepted the one-China policy since it reached its 1992 Consensus with Beijing.

Tsai, who won a landslide victory over her KMT opponent in a January presidential election, has refused to recognise that consensus since coming to power.

Analysts have warned Trump’s intent to use the issue as leverage to win compromises by Beijing on other areas might not be wise.

“His gambit is unlikely to succeed,” said Bonnie Glaser, director of the China Power Project at the Centre for Strategic and International Studies, while Weiss warned it was “likely to backfire”.

Xiaoyu Pu, a professor of international relations with the University of Nevada, Reno, said it was just a bargaining tactic by Trump: “I doubt he can fundamentally change the one-China policy”, while Baogang Guo, a professor of international relations at Dalton State College, said Trump’s goal was to maximise US economic interests.

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The need for a “one China” understanding came about after the end of the Chinese civil war in 1949, when Chiang Kai-shek’s nationalists were defeated by Mao’s communists and fled to Taiwan, leading to the existence of the People’s Republic of China on the mainland and the Republic of China in Taiwan.

The policy is held to so tightly by China’s leaders because it also underlines the legitimacy of communist rule in the country. Under the policy, any country wishing to establish diplomatic relations with Beijing must also sever all formal ties with Taipei.

Washington’s acceptance of this principle was seen as the condition for the contact between the two nations re-established by Richard Nixon and Mao in 1972. It was also the foundation for the formalisation of diplomatic ties agreed by Jimmy Carter and Deng Xiaoping (鄧小平) in 1979. In the Shanghai Communiqué signed at the end of Nixon’s visit in February 1972, the US acknowledged that “all Chinese on either side of the Taiwan Strait maintain there is but one China and that Taiwan is a part of China”.

In a joint communiqué announcing the formalisation of diplomatic ties in 1979, Washington reaffirmed that it acknowledged “the Chinese position that there is but one China and Taiwan is part of China”. At the same time, it cut formal diplomatic relations with Taipei and closed its embassy there.

Following Beijing’s resumption of its seat in the United Nations Security Council, replacing Taipei, in 1971, and Nixon’s China visit in 1972, there was a worldwide scramble of nations shifting diplomatic relations from Taipei to Beijing. Today, just 22 countries or entities have full diplomatic relations with the Republic of China.

And ever since Nixon’s visit, the triangular relationship between Washington, Beijing and Taipei has been a diplomatic challenge as complex as it is important. While Washington and Beijing have often disagreed over such issues as trade, currency and human rights, it is their often differing interpretations of the subtle one-China principle that has been at the centre of some of the most notable episodes of discord in the past four decades.

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Soon after Washington and Beijing normalised diplomatic relations, the US Congress passed the Taiwan Relations Act (TRA), affirming important unofficial ties with the island. The new legislation replaced the previous bilateral defence treaty, offering a qualified commitment to the island’s security and providing for the supply of necessary “defence articles and services”.

US arms sales to Taiwan, totaling more than US$46 billion since 1990, have led to US-China friction and an upsurge in bellicose rhetoric across the strait.

Some analysts believe Trump’s questioning of the one-China policy might also signal his intent for more arms sales to Taiwan. In particular, his tweets have spurred speculation over whether the US might sell the long anticipated F-16C/D fighter jet to Taiwan.

Jingdong Yuan, a regional security expert with the University of Sydney, said new US arms sales to Taiwan could trigger a major backlash, including the suspension of dialogues and cooperation on Iran and North Korea.

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He said Beijing was also likely to punish Taiwan economically, possibly by conducting naval military exercises that would border on a blockade, or by otherwise disrupting maritime economic ties between Taiwan and its key trading partners. It would also launch diplomatic offensives to further reduce the number of countries that recognise Taipei.

There have been plenty of flashpoints previously in relation to the one-China issue, notably when Beijing was enraged by a US decision to grant the independence-leaning Taiwanese President Lee Teng-hui a visa in 1995. In response, the People’s Liberation Army fired missiles into the waters off Taiwan, prompting Bill Clinton to dispatch two aircraft groups to sail through the Taiwan Strait.

Analysts warned similar crises might lie ahead if Trump continued to challenge the status quo.

David Zweig, director of the Centre on China’s Transnational Relations at Hong Kong University of Science and Technology, described the one-China policy as a core principle of China’s national identity, a fundamental pillar of US-China relations, and a key component of the Communist Party’s legitimacy. Given this, he said, the question of sovereignty over Taiwan could absolutely not be used as a bargaining chip to gain concessions. “Challenges to China’s sovereignty, particularly on Taiwan, are infinitely more sensitive, non-negotiable, and strategically destabilising than other issues,” Zweig said.

WATCH: China warns Trump on Taiwan comments

Guo, at Dalton State College, added: “Any change in US policy in this area may disturb the political and military stability in the Taiwan Strait and lead to another round of the Taiwan Strait crisis.”

While some pro-independence forces in Taiwan have been encouraged by Trump’s rhetoric, seeing it as a rare historic chance to alter the status quo, most analysts warn of dire consequences on the island.

“Ditching the one-China policy will make Taiwan less secure since it will cross Beijing’s red line, and Beijing will be compelled to respond resolutely,” said Zhiqun Zhu, director of the China Institute at Bucknell University.

In addition to opposing US positions on international issues such as Syria and North Korea, Beijing has plenty of other options in retaliating against the US: it can make life difficult for US companies operating in China, sell US treasury bills, restrict repatriation of earnings, cancel orders for Boeing passenger planes and recall its ambassador. And while President Xi Jinping ( 習近平 ) has – for now – remained patient, no one expects the nationalistic strongman leader to back down on questions of sovereignty. Xi recently told a visiting KMT delegation his party would be “overthrown” if it allowed Taiwan to become independent.

Warren Sun, professor of Chinese Studies at University of Monash, said a new foreign policy by Trump towards China could post the biggest threat to Xi’s leadership domestically. “The Trump administration is bound to cause problems for the Xi administration,” Sun said, adding that his campaign theme of “making America great again” was inherently on a collision course with Xi’s “China Dream” platform that promises China a similar return to fortune.

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He described Xi as facing one of the greatest diplomatic challenges of the post-Mao period and said some kind of “clash of the titans” appeared unavoidable.

Zweig, at HKUST, said Xi’s world view, and domestic pressures, would leave him little choice but to respond with highly provocative military measures. If Zweig is right, what may have started as a misconceived gambit by a US leader seeking a vague and undefined economic advantage could end as an armed confrontation that spells disaster for the world.