By Trevor Hunnicutt and Sakura Murakami TOKYO (Reuters) -U.S. President Joe Biden said on Monday he would be willing to use force to defend Taiwan against Chinese aggression in a comment that seemed to stretch the limits of the ambiguous U.S. policy towards the self-ruled island. While Washington is required by law to provide Taiwan with the means to defend itself, it has long followed a policy of “strategic ambiguity” on whether it would intervene militarily to protect Taiwan in the event of a Chinese attack. After Biden made the remark at a joint news conference with Japanese Prime Minister …