The most eye-catching part of the legislation is the proposed designation of Taiwan as a “major non-Nato ally”, meaning it would be viewed as one of Washington’s closest global partners, especially on trade and security cooperation.

That “would be equivalent to recognition of Taiwan’s sovereignty. It means that the US would abandon its China policy completely”, Lu said. “Recognising Taiwan’s sovereignty means recognising its independence, and as a result, China would have to resolve the Taiwan issue once and for all.”

Wu Xinbo, dean of the Institute of International Studies at Shanghai’s Fudan University, also said the bill could be more of a challenge than Pelosi’s trip.

“If Washington follows the current path on Taiwan, I think it would effectively lead to some sort of restoration of the US-Taiwan military alliance,” he said. “That would be seen as a direct challenge to the very basis for the establishment of US-China ties, and China would almost definitely react more fiercely than it has this time.”

Touted as “the most comprehensive restructuring of US policy towards Taiwan” since Beijing and Washington established official ties in 1979, the bill tries to bolster the island’s defence capabilities with security aid of US$4.5 billion and promises to support its participation in international organisations.

It represents “a clear message to Beijing not to make the same mistakes with Taiwan that [Russian President] Vladimir Putin has made in Ukraine”, said US Senate Foreign Relations Committee chairman Bob Menendez, who co-sponsored the legislation with Republican Senator Lindsey Graham.

The bill, which has been delayed several times since its introduction in June, comes at a sensitive time for bilateral ties, which hit a new low over Pelosi’s visit and Beijing’s subsequent sabre-rattling.

US President Joe Biden on Monday voiced concerns about the People’s Liberation Army’s days of drills around Taiwan. US officials denounced the exercises that including ballistic missile launches over the island, accusing Beijing of trying to change the status quo in the Taiwan Strait and destabilising the region.

What defence dialogues did Beijing cancel after Pelosi’s Taiwan trip?

In addition to the drills, Beijing has also halted bilateral talks with Washington on defence and climate change and imposed retaliatory sanctions on Pelosi, prompting fears of a new Taiwan Strait crisis.

According to Lu, the legislation would mark “a radical change” in Washington’s position on the sensitive Taiwan question, which Beijing claims is the most important bilateral issue in US-China relations.

Beijing considers Taiwan part of its own territory that must be taken back, by force if necessary, and it opposes any official exchanges between the island and Washington.

Wu said Beijing could go further with its military intimidation of Taiwan in response to the legislation, sending fighter jets over the island, or recall its ambassador to the US, which would be an effective downgrading of bilateral ties.

Experts are pessimistic about the prospects for ties between Beijing, Washington and Taipei, given the likelihood of Republicans controlling both houses of Congress following the midterm elections, which could lead to the introduction of more pro-Taiwan legislation.

Andrew Mertha, director of the China studies programme at the Johns Hopkins School of Advanced International Studies, said Pelosi’s visit and China’s unprecedented military response had put the Biden administration in “a terrible bind”.

“It will be impossible politically for him to deny an upgrading of assistance to Taiwan, given the bipartisan hawkishness on China on [Capitol] Hill … which Pelosi has now further cemented,” he said. “But doing so will be seen by Beijing as further eroding the one-China policy, following Biden’s comments in recent months on [defending] Taiwan.”

Mertha also warned that Pelosi’s visit had substantially eroded mutual trust between Beijing and Washington, making necessary bilateral cooperation and engagement a lot more difficult, if not impossible.

But Matt Abbott from the Chicago Council on Global Affairs played down the significance of the bill.

“The relationship between China and the US has been deteriorating for several years now, well before this legislation was introduced and Speaker Pelosi’s visit to Taiwan,” he said.

“While many of the provisions in the legislation will undoubtedly upset the Chinese government, it does still include language explicitly reaffirming that it is not to be construed as a restoration of diplomatic relations with Taiwan. It also is noted that it does not change the US government’s position on Taiwan’s international status.”

Robert Sutter, a veteran China expert at George Washington University, said it was too early to make predictions about the impact of the bill, which, pending Senate reviews, would largely depend on its final wording.

He said the proposed legislation could use non-binding language like the Taiwan Relations Act adopted in 1979. Along with its one-China policy, Washington regards the TRA – which Sutter said had no binding language largely because of administration and congressional interventions – as the basis of its Taiwan policy.

Sutter said if the bill contained binding language that would substantially change US government actions regarding Taiwan, it could have long-term and serious implications.

“I suspect the administration and the many members of Congress who don’t want US-China tensions to rise more at this time will try hard to insert language in the draft bill that would make its provisions non-binding, allowing the administration to continue to conduct US policy along lines it sees in accord with the very broad ranging and arguably vague US one-China policy,” Sutter said.

He said if a bill were to pass without binding language, it would “anger Beijing at a sensitive time” and perhaps worsen tensions. “But Chinese officials responsible for Taiwan affairs would understand the bill’s symbolic status does not advance US government actions in serious ways,” he said.

Additional reporting by Minnie Chan