U.S. Secretary of State John Kerry is trying to head off another international crisis and is urging China and its smaller neighbors to peacefully resolve mounting tensions over maritime disputes in Asian waters.

Speaking to the foreign ministers of China and the 10 members of the Association of Southeast Asian Nations, Kerry said Sunday it's not enough to simply continue working on a long-delayed binding code of conduct for the South China Sea where many have competing claims to territory.

Kerry is urging the nations to resolve questions about their claims, noting that uncertainty creates risks for heightened tensions.

He says that the obligation to make claims clear applies to all the parties, not just China.