The de facto U.S. ambassador in Taipei joined for the first time on Sunday a Taiwanese leader, amid rising tensions with Beijing, to commemorate a key military clash and the last time Taiwanese forces joined battle with China on a large scale.

China, which claims Taiwan as its own, has stepped up military activity around the democratic island, moves denounced by Taiwan's government as an attempt at intimidation to force them to accept Chinese rule.

Taiwan President Tsai Ing-wen laid a wreath and bowed her head in respect at a memorial park on Kinmen island, which sits a few kilometers off the Chinese metropolis of Xiamen, to mark the 62nd anniversary of the start of the second Taiwan Straits crisis.