US President Joe Biden on Tuesday said there was no change to a US policy of "strategic ambiguity" on Taiwan, a day after he angered China by saying he would be willing to use force to defend the island. The issue of Taiwan loomed over a meeting in Tokyo of leaders of the Quad grouping of the US, Japan, Australia and India, who stressed their determination to ensure a free and open Indo-Pacific region in the face of an increasingly assertive China - though Japanese Prime Minister Fumio Kishida said the group was not aimed at any one country. All four leaders shared concerns about Ukraine....