The US is concerned that China is flirting with the idea of seizing control of Taiwan as President Xi Jinping becomes more willing to take risks to boost his legacy.

“China appears to be moving from a period of being content with the status quo over Taiwan to a period in which they are more impatient and more prepared to test the limits and flirt with the idea of unification,” a senior US official told the Financial Times.

The official said the Biden administration had reached the conclusion after assessing Chinese behaviour during the past two months.

“As we prepare for a period in which Xi Jinping will likely be entering his third term, there’s concern that he sees capstone progress on Taiwan as important to his legitimacy and legacy,” the official added. “It seems that he is prepared to take more risks.”

Twenty Chinese warplanes flew into Taiwan’s air defence zone on Friday, marking its biggest incursion. It came one day after the US and Taiwan agreed to boost co-operation between their coast guards.

The rising alarm in the Biden administration matches a warning from Admiral Philip Davidson, head of US Indo-Pacific command, who told senators China could take military action “in the next six years”.

Admiral John Aquilino, who is scheduled to succeed Davidson, this week told Congress that there was a wide range of forecasts but “my opinion is this problem is much closer to us than most think”.

Aquilino said China had taken other “aggressive actions”, including clashes with India on their border that suggested it was emboldened.

“We’ve seen things that I don’t think we expected,” Aquilino told the Senate armed services committee.

“That’s why I continue to talk about a sense of urgency. We ought to be prepared today.”

Kurt Campbell, the top White House Asia official, told the FT that while China was acting in an increasingly aggressive manner in many areas, it was taking the most assertive activities in its approach to Taiwan.

“We have seen China become increasingly assertive in the South China Sea . . . economic coercion against Australia, wolf warrior diplomacy in Europe, and the border tensions with India,” he said.

“But nowhere have we seen more persistent and determined activities than the military, diplomatic and other activities directed at Taiwan.”

The FT reported in January that Chinese fighter jets and bombers simulated missile attacks on the USS Theodore Roosevelt aircraft carrier three days after Joe Biden was inaugurated as US president.

The simulation occurred as Chinese warplanes spent two days flying in and out of Taiwan’s air defence zone just days after Biden was sworn in, in what was the largest Chinese exercise in the area until the intrusion on Friday. One US defence official said the incident was not the first time China had simulated attacks on US ships.

Taiwanese national security officials say they are concerned that the Chinese Communist party’s next congress in 2022 — key to confirming Xi’s extended position as the Chinese leader for a third term — and the centenary in 2027 of the founding of the People’s Liberation Army could be points at which Xi feels compelled to make a move on Taiwan.

But in general, the growing US concern is not echoed as loudly in Taipei. One senior Taiwanese official said China had raised its military pressure on Taiwan, but there was no sign of an imminent attack.

Separately, Alexander Huang, a former deputy chair of the Mainland Affairs Council, Taiwan’s cabinet-level China policy body, said there was a “crazy perception gap” that was “dangerous”.

The rising US concern about Taiwan comes as US-China relations show no sign of improving. Antony Blinken, secretary of state, and Jake Sullivan, national security adviser, last week held a meeting in Alaska with Yang Jiechi, the top Chinese foreign policy, and Wang Yi, foreign minister, which started with an extraordinary public spat.

In his opening remarks, Blinken said the US would raise concerns in private about issues that “threaten the rules-based order that maintains global stability” including Chinese actions towards Taiwan. Yang fired back by lambasting the US and pledging that China would “take firm actions in response” to any interference regarding Taiwan.

US officials said they had more cordial discussions in private after the public “theatrics”. Several people familiar with the talks said the US team rebuffed Chinese efforts to “reset” the relationship via the creation of strategic dialogues, which was one of the Chinese goals for the first high-level meeting under the Biden administration.

Towards the end of the Alaska meeting, Yang told Blinken and Sullivan that he hoped to welcome them in Beijing for more discussions. According to people familiar with the situation, Blinken leaned across the table and said, “thank you”, which prompted a discussion on the Chinese side about whether the US was accepting the invitation.

After the Chinese had conferred for some time, Yang asked Blinken what he meant by “thank you” and whether his reply meant the US negotiators were prepared to hold follow-on discussions in Beijing.

“Thank you means thank you,” Blinken replied, signalling to Yang and Wang that the answer for now was “No”.

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