But the speech triggered an immediate response by President Tsai Ing-wen, who said Taiwan would never accept the “one country, two systems” model suggested by Xi, adding that people on the island resolutely opposed it.

In the open letter released on Tuesday, 44 mainly US-based academics said that in the past two years Beijing “has left no stone unturned in its attempts to squeeze Taiwan’s international space, threaten it with a build-up of military power, and made it appear as if Taiwan’s only future lies in integration with an authoritarian China”.

The signatories included Jerome Cohen, a New York University law professor and former teacher of Tsai’s predecessor Ma Ying-jeou; Stephen Young and William Stanton, two former directors of the American Institute in Taiwan; and Bruce Jacobs, a professor emeritus at Australia’s Monash University.

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The letter also warned the island’s people to stay alert to mainland intrusion because “if Taiwanese across the political spectrum fail to understand this threat, and go on with business as usual, this provides Beijing’s repressive leaders with an opportunity to divide Taiwanese society, and increasingly make it an inevitability that Taiwan is incorporated into China”.

In a separate letter, representatives of Taiwan’s indigenous communities rejected the view that they formed a minority within the “Chinese nation”.

“Taiwan is the sacred land where generations of our ancestors lived and protected it with their lives. It has never belonged to China,” said the community in the letter.

“We have never given up our rightful claim to the sovereignty of Taiwan,” it added, “the Taiwanese indigenous peoples will not be threatened and will make no concessions.”

Taiwan first saw mass Han immigration from the mainland during the 17th century at the end of which it was brought under the rule of the Qing dynasty. It was ruled by Japan between 1895 and 1945 and, following the Chinese civil war, the defeated Nationalist government and around two million people fled from the mainland.

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Han Chinese now make up around 95 per cent of the population and Beijing has never ruled out the use of force to reunify the island with the mainland.

Tian Feilong, the executive director of the one country two systems legal studies centre at Beihang University’s law school in Beijing, said the two open letters highlighted dramatic differences in attitudes across the Taiwan Strait.

“Beijing has to learn from these two letters that [Tsai’s] Democratic Progressive Party’s stance on independence has support from both society and academics.

Tian added that Beijing needed more than its “long-repeated” 1992 consensus on cross-strait relations – which affirmed the “one China” principle without clarifying what that means – to convince the Taiwanese people.

Chang Ya-chung, a political scientist at National Taiwan University, said people’s fears about Beijing were because people did not “fully understand what Beijing was saying about unification”.

“Xi was trying to say Beijing is willing to discuss everything with Taipei, but at present unification only means a forced takeover to Taiwan, since Taiwan is so small compared with the mainland,” Chang said.