On US President Joe Biden’s tour of Asia, one issue threatened to spark the already acrimonious relationship between Washington and Beijing. Taiwan, which China considers part of its territory and for whose unification it does not renounce the use of force. The United States is required by law to supply weapons for the democratic-ruled island’s self-defense, but for four decades it has shied away from clarifying whether it would come to Taipei’s aid in the event of an invasion, in a policy it calls “strategic ambiguity.” Biden has pushed that button. Asked Monday by a reporter if he would defend Taiwan in the event of an attack, the White House tenant said “yes.” “It’s the commitment we’ve made,” he added.

“We respect the One China policy. We have signed it, her and all the agreements made from her,” he said. “But the idea that [Taiwan] can be taken by force, simply by force, is not appropriate,” Biden stressed that his expectation is that something like this would not happen or be attempted.

The expression “One China” represents – albeit with different interpretations – the basis of diplomatic relations between Beijing and the United States (and between Beijing and other nations). For the Asian giant, that expression is a “principle” and implies the recognition that there is only one China, and this includes Taiwan, where the nationalist troops defeated by the communist army in the civil war in 1949 took refuge. For the United States, the expression is a “policy” and means that it recognizes the government in Beijing as China’s representative, but Taiwan’s status is not determined.

Later, a White House official accompanying Biden qualified that the presidential response does not mean an abandonment of “strategic ambiguity.”

It is not the first time that the Democratic president has issued statements in which he is willing to provide military assistance to Taiwan in the event of an attack. Already in October, he made a similar comment, which caused enormous unrest in Beijing before White House officials clarified – as now – that there has been no change of American position. The Taiwanese issue is the most important, and most sensitive, issue in the U.S.-China relationship; Beijing warns Washington again and again against its support for the island.

Since Chinese President Xi Jinping came to power, and especially since the beginning of President Tsai Ing Wen’s term in Taipei in 2016, Beijing has increased its pressure on the island. Chinese military jets frequently fly over Taiwanese air defense space, and the Xi government’s rhetoric is increasingly assertive about future unification, albeit by force. At the same time, he maintains that his preference is unification by peaceful means, through increasing economic, political, and cultural relations.

In Beijing, China has reiterated the position it usually claims in everything related to Taiwan: “No one should underestimate the firm determination, firm will and ability of the Chinese people to defend national sovereignty and territorial integrity,” Chinese Foreign Ministry spokesman Wang Wenbin said at his ministry’s daily press briefing.