“There cannot be a situation where a bigger nation is simply allowed to bully smaller nations,” he told reporters in Beijing, where Obama attended the summit.
Singapore sees the maritime disputes as one of the region’s biggest threats to security, Foreign Affairs Minister K Shanmugam told reporters.
Singapore will push for progress on a code of conduct that will reduce the potential for disruption to trade, he said.
Obama will use talks with Myanmar President Thein Sein to push for changes to the apartheid-like living conditions of Myanmar’s ethnic Rohingya minority, as well as democratic reform.
Myanmar’s military-drafted constitution bars opposition leader Aung San Suu Kyi from becoming president. Obama will meet Suu Kyi in the city of Yangon on Friday.