Tsai's remarks, pre-recorded and delivered to a U.S. audience at a Washington forum, come after U.S. President Joe Biden pledged in September to defend Taiwan in the event of any "unprecedented attack" by China.Though the White House has said Biden's pledge did not signify a change in U.S. policy, critics argue he may have undercut – intentionally or not – a U.S. stance of not taking a position on Taiwan's independence.James Moriarty, the U.S.-based chairman of the American Institute in Taiwan, Washington's de facto embassy in Taipei, said "strategic ambiguity" over whether Washington would come to the island's defense had never been stated as policy in any documents.Referring to the decades-old Taiwan Relations Act, which forms the basis of the United States' unofficial ties with Taiwan, he said: "The original documents make it clear that we would have to do something if there is an attempt to change Taiwan's status by force."Moriarty added that he did not think Chinese leader Xi Jinping had set a deadline of 2027 to take Taiwan, only that China's military should have the capability to do so by then."