In a Monday press conference in Tokyo, the American president was asked if—in contrast to the U.S.’s unwillingness to get involved militarily in Ukraine—he was “willing to get involved militarily to defend Taiwan if it comes to that.”

“Yes,” said Biden. “That’s the commitment we made.”

The U.S. has for decades maintained a stance of “strategic ambiguity” regarding the defense of Taiwan, a semiconductor powerhouse that Beijing sees as a breakaway province.

Washington gave diplomatic recognition to Beijing rather than Taipei in 1979, while also establishing an unofficial relationship with Taiwan, with a legal commitment to “provide Taiwan with arms of a defensive character and…maintain the capacity of the United States to resist any resort to force or other forms of coercion that would jeopardize the security, or social or economic system, of the people of Taiwan.”

A few years later, the U.S. promised China that it would phase out arms sales to Taiwan, but also assured Taiwan that it would set no end date for those sales.

Monday’s comment is not the first time Biden has appeared to abandon the strategic-ambiguity balancing act. Last October, he also said “We have a commitment to do that,” when asked if the U.S. would come to Taiwan’s defense. White House Press Secretary Jen Psaki subsequently insisted Biden had not announced any change in policy, but Beijing warned he should “avoid sending wrong signals to the ‘Taiwan independence separatist forces.'”

In November, Biden arranged a meeting with Chinese President Xi Jinping, at which—in the White House’s words—he “underscored that the United States remains committed to the ‘one China’ policy.”

However, there is more than one ‘one China‘ policy. Beijing’s version says Taiwan is part of the People’s Republic of China; the U.S.’s only acknowledges that view, without necessarily agreeing with it.

The Taiwan issue has taken on new urgency in recent months, largely due to Russia’s invasion of Ukraine. With Russia and China being strategic partners, some fear Russian success in Ukraine could embolden China to attempt a military seizure of Taiwan.

In March, soon after the Russian invasion began, Biden sent a group of former senior security and defense officials to Taiwan, to underscore that the U.S. “stands firm behind its commitments.”

And earlier this month, the U.S. State Department triggered angry exchanges with China’s foreign ministry by heavily revising its fact sheet on U.S. relations with Taiwan.

While the previous, Trump-era version of the fact sheet said “the United States does not support Taiwan independence,” the new version removed that language. It also dropped language reiterating how the U.S. acknowledges “the Chinese position that there is but one China and Taiwan is part of China,” and added wording saying “the United States has a longstanding one China policy” based on the 1979 and 1982 agreements.

“The U.S.’ latest modification of the fact sheet is a trick to obscure and hollow out the one-China principle. Such political manipulation of the Taiwan question and the attempt to change the status quo across the Taiwan Strait will hurt the U.S. itself,” said Chinese foreign ministry spokesperson Zhao Lijian on May 10.

On the weekend, Chinese Assistant Minister of Foreign Affairs Hua Chunying warned that “misrepresenting” the one-China principle “could bring the whole edifice of China-U.S. relations crashing down and undo the hard-won progress of the last four decades.”

When Biden made his Taiwan-defense comment on Monday, the White House press team again leaped in to insist that he meant no change in U.S. policy. However, even that partial walk-back reflected the Biden administration’s recent change in tone on which one China policy takes precedence: “He reiterated our One China Policy and our commitment to peace and stability across the Taiwan Strait.”