China and Vietnam have been engaged in a tense standoff since China positioned an oil rig in disputed waters May 1. Both sides have accused the other of ramming ships. Vietnam has presented a video showing Chinese ships hitting its vessels.
"We want to see a code of conduct created; we want to see this resolved peacefully through the Law of the Sea, through arbitration, through any other means, but not direct confrontation and aggressive action," Kerry said before a meeting at the State Department with Singapore foreign minister K Shanmugam.
Shanmugam echoed Kerry's desire for Southeast Asian nations and China to agree on a code of conduct for the South China Sea, an effort to help manage territorial disputes that involve China and five other claimants.
"We need a situation where parties resolve their disputes and their differences in a way that's acceptable to all," he said.
The US says it takes no stance on the sovereignty disputes, but has an interest in open commerce and navigation in the South China Sea, which is crisscrossed by busy shipping lanes.