BEIJING • Sao Tome and Principe's recent switch in diplomatic recognition from Taiwan to China is, to many, Beijing punishing Taipei for not adhering to the "one China" principle and attempting to tread a Taiwan independence path in the international arena.

But it is likely also a signal to United States President-elect Donald Trump that it benefits no one, least of all Taiwan, if he were to overturn Washington's decades-old "one China" policy.

Sao Tome's severing of diplomatic ties with Taiwan and China's re-establishing of ties with the African state came less than a month after Mr Trump spoke on the phone with Taiwanese President Tsai Ing-wen on Dec 2 last year, breaking with a nearly four-decade-old tradition of no direct contact between top leaders of the two sides.

China had at the time trained its crosshairs on Taiwan, calling the 10-minute phone conversation a "petty gambit" by the government of the island it regards as a breakaway province to be reunified at some point in time.

About a week later, when asked about the phone call, Mr Trump questioned his country's "one China" policy, which had underpinned Sino-US relations since Washington switched diplomatic ties from Taiwan to China in 1979.

"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," he said to news channel Fox News.

China's reaction to Mr Trump's remarks was also measured, with its Ministry of Foreign Affairs spokesman Geng Shuang saying: "We are seriously concerned about it. The Taiwan question has a bearing on China's sovereignty and territorial integrity and is one of China's core interests."

And China has every reason to be concerned.

For through its "one China" policy, Washington recognises Beijing as the sole government of China. It also acknowledges China's position that there is only one China and that both the mainland and Taiwan belong to that one China - also known as the "one China" principle.

The policy effectively puts Taiwan out in the cold diplomatically, because it is not just the US, but also the United Nations and most of the countries in the world that do not recognise Taiwan as a state. Taiwan has only 21 diplomatic allies after Sao Tome switched recognition, many of them small and impoverished states in Latin America, Africa and the South Pacific.

In Washington's case, its recognition of China is balanced by its Taiwan Relations Act of 1979 that sought to ensure Taiwan's security by authorising the sale of arms to the island and requiring the executive branch to "inform the Congress promptly of any threat to the security or the social or economic system of the people on Taiwan and any danger to the interests of the United States arising therefrom". The US also insists on the peaceful resolution of the cross-strait issue while not supporting Taiwan's independence.

In practical terms, while the US and Taiwan do not have diplomatic ties, Washington maintains close cultural and economic ties with the island and has a de facto embassy, the American Institute in Taiwan (AIT), through which it interacts with the Taiwan government.

Importantly, the US "one China" policy is accompanied by a set of unstated guidelines, as noted by former AIT chief Richard Bush in his book Untying The Knot - Making Peace In The Taiwan Strait.

These are "preventing a military imbalance between China and Taiwan; discouraging provocation by either side; discouraging both overconfidence and a lack of confidence; maintaining public support in the United States for US policies; and maintaining some degree of ambiguity on the US use of force", wrote Dr Bush.

Through its "one China" policy and the accompanying guidelines, the US has maintained a delicate balance between its ties with China and Taiwan, at times disappointing one or the other side but never upsetting the apple cart.

The closest the two sides came to a confrontation over Taiwan was in 1995-1996 after then Taiwanese President Lee Teng-hui visited the US in June 1995. The visit led to a deterioration in the US-China relationship and China's missile exercises in the Taiwan Strait in the run-up to the Taiwanese presidential election in March 1996. The US sent two aircraft carrier battle groups to the Taiwan area to show its resolve to protect Taiwan and to avoid any accidental conflict.

Now that Mr Trump has called the "one China" policy into question, many are led to wonder if he will renege on it. This will likely cause nervousness not only in Beijing but also in Washington and Taipei.

Dr Bush, now a senior fellow at the John L. Thornton China Centre, was moved to write an open letter to Mr Trump in which he warned that doing so "would not provide leverage on trade, North Korea, the South China Sea, or any of the other issues that roil the (US-China) relationship. More likely, it would rattle the entire framework of the relationship, and cause Beijing to rethink its policy of seeking reunification by peaceful means".

In Taipei, those supportive of Taiwan's independence applauded Mr Trump's remarks.

Writing in the Taipei Times newspaper, former legislator Parris Chang said "it makes sense that Trump is questioning the 'one China' principle as the US does not support China's stance. Although it recognises that the People's Republic of China government is representative of China, it does not recognise (that) Taiwan belongs to China".

He predicted that high-level talks between Taiwan and US officials would become easier as ties between the two sides were expected to improve.

"Beijing hawks have warned that, if the US improves relations with Taiwan, China would punish the latter by imposing economic sanctions or buying off its diplomatic allies. However, the US will not stand by and watch Beijing bully Taiwan or annex it by military force," he wrote.

But there are those who warned against being used as a bargaining chip by Mr Trump in the US' interest.

"Trump is using words to irritate China in the hope of getting China to come to the negotiating table, but the danger is that he is raising false hopes that he has Taiwan's interests at heart when in fact he does not," said Taiwanese political analyst Yen Chen-shen.

Taiwanese analyst Edward Chen warned that Mr Trump "will have no qualms selling Taiwan out".

China's Taiwan Affairs Office spokesman An Fengshan said "upholding the 'one China' principle is the political basis of developing China-US relations".

Interfering with or damaging this basis would mean that "the healthy, stable development of China-US relations is out of the question and peace and stability in the Taiwan Strait will be seriously impacted", he added.

It is anybody's guess what Mr Trump will do with regard to the "one China" policy once he assumes office on Jan 20.

But some adjustment to the US' Taiwan policy is possible, given that there are some Taiwan-friendly individuals in Mr Trump's Cabinet, including incoming chief of staff Reince Priebus and trade chief Peter Navarro.

With the Chinese characterising the Taiwan issue as the "most sensitive and complicated issue in China-US relations", Washington and Beijing are set to enter an uneasy period in their relationship and, for the Taiwan Strait, one of greater uncertainty.