US Secretary of State John Kerry on Monday urged progress on a code of conduct to govern the hotly disputed South China Sea, after ally the Philippines warned of a Chinese military build-up in the strategically vital waters.
"We very much hope to see progress on a substantive code of conduct to help ensure stability in this vital region," Kerry told foreign ministers of Southeast Asian nations at a meeting in Brunei.
Kerry reiterated that the United States does not take a stand on the sea's myriad disputes, many of which pit a rising China against its neighbours.
But Kerry said: "We have a strong interest in the manner in which the disputes of the South China Sea are addressed and in the conduct of the parties."
"As a Pacific nation and a resident power, the United States has a national interest in the maintenance of peace and stability, respect for international law, unimpeded lawful commerce and freedom of navigation in the South China Sea," Kerry said.
But he said, in a clear reference to China: "Our actions are not intended to contain or to counterbalance any one country."
China has been reluctant to reach a code of conduct with the ASEAN bloc, preferring to negotiate individually with each country.
The Philippines and Vietnam have in recent years accused China of increasingly aggressive actions to exert claims to the sea.
China insists it has sovereign rights to all of the sea. ASEAN members the Philippines, Vietnam, Brunei and Malaysia, as well as Taiwan, also claim parts of the sea.
On Sunday, Philippine Foreign Secretary Albert Del Rosario told his ASEAN colleagues in Brunei that China had begun a "massive" military build-up in the sea.
"The overwhelming presence of Chinese ships, including military and paramilitary ships, and the issuance of threats pose serious challenges for the region as a whole," Del Rosario said.
Kerry's predecessor, Hillary Clinton, made similar statements on the US position on the South China Sea, starting at a 2010 ASEAN meeting in Hanoi.
Those comments signalled stronger US support for Southeast Asian nations at a time of tension with China.
Kerry, who flew straight into meetings after exhaustive diplomacy in the Middle East, rejected suggestions that President Barack Obama's administration would focus less on Asia after Clinton's departure.
"Let me be crystal clear. I know that some people wondered whether in the second term of the Obama administration and with a new secretary of state, are we going to continue on the path that we have been on?
"The answer, I say to all of you directly, is yes -- not just yes, but we hope to increase the effort," Kerry said.