https://en.wikipedia.org/wiki/First_Taiwan_Strait_Crisis
However, after the outbreak of the Korean War on 25 June 1950, Truman declared that the "neutralization of the Straits of Formosa" was in the best interest of the United States, and he sent the U.S. Navy's Seventh Fleet into the Taiwan Strait to prevent any conflict between the Republic of China and the People's Republic of China, effectively putting Taiwan under American protection. The move was also intended to deter ROC attacks against the Chinese Mainland.
没看出放弃。他要保证大陆和台湾不给他再添麻烦。你要大陆如何这时统一台湾呢?
本来毛泽东本就倾向于统一台湾。这一步就是美国逼着中国最后参战朝鲜战争去的一个因素。