US allies in Asia are increasingly concerned that President Donald Trump could soften Washington's position on Taiwan to secure an economic agreement with Chinese leader Xi Jinping at their expected September 24 summit. The concerns intensified after Trump described a $14 billion Taiwan arms package as a negotiating chip and amid efforts to recover approval ratings dented by the Iran war. Taiwan, Japan and US officials and analysts say even a subtle change in US rhetoric could embolden Beijing and threaten regional stability. China regards Taiwan as the core of its interests, has not renounced force to bring the island under its control and is expected to raise the issue with Trump. Washington's one China policy (a framework that avoids recognizing Taiwan as sovereign) takes no official position on Taiwan's sovereignty while acknowledging Beijing's position. Trump has said Xi assured him China would not attack Taiwan during Trump's term, but unlike Joe Biden, Trump has declined to say whether the US would defend the island. Japan and Taiwan are seeking reassurance before the summit, while Beijing is pressing Washington to take its concerns over arms sales seriously. Analysts also warn that a conflict would have global economic consequences because Taiwan produces over 90% of the world's advanced semiconductors.