As the strategic competition between the United States and China intensifies, South Korea is facing growing pressure to chart an optimal diplomatic strategy to navigate the convoluted geopolitics and foster lasting peace on the Korean Peninsula and beyond. At this crucial juncture, this study examines multi‐faceted, capacity‐building measures for peace aimed at precluding Sino–US friction in the East and South China Seas from spilling over into the Korean Peninsula. This article presents a road map to stimulate and reinvigorate security cooperation among South Korea, the United States, and Japan and economic cooperation among South Korea, China, and Japan in a virtuous cycle, and by extension to craft a dialogue channel among South Korea, the United States, and China. It also puts forward a three‐stage program for the evolution of the South Korea–US alliance whereby South Korea secures flexibility in its approach to China based on the robust trust of the alliance. This is to enable South Korea to assume a key role in connecting the three trilateral cooperation channels with the development of the Seoul–Washington alliance being a key driver to expand Seoul's diplomatic capacity. In the end, this study envisions a foreign policy model for South Korea that would allow the middle‐power country to punch above its weight by expanding the framework of cooperative security. It aims to ultimately pursue a multilateral, common security architecture in Northeast Asia, including China, which will serve as a multilayered catalyst to promote lasting peace on the Korean Peninsula.