The U.S. wants Asian allies to stand up to China. It’s not that easy

SINGAPORE — Seeking support in a budding cold war with Beijing, the U.S. is looking to Southeast Asia, where longstanding allies and security partners have clashed with their giant neighbor in the resource-rich South China Sea. China’s claims over nearly the entire waterway — impeding fishing and oil exploration, sinking smaller countries’ vessels and inciting military confrontations — were ruled illegal by an international tribunal in 2016. The State Department formally endorsed that ruling this week, denouncing China’s “completely unlawful” claims and “bullying” of rivals. The bristling, 750-word statement marked a significant policy shift by the U.S., spelling out for the first...