China and the 10-member Association of Southeast Asian Nations signed a nonbinding edict eight years ago that called for a peaceful resolution of competing claims to ownership of the Spratlys in the South China Sea and a freeze on any steps that could spark fighting.

The United States is concerned that the dispute could hurt access to one of the world’s busiest commercial sea lanes. President Barack Obama and ASEAN leaders recently reiterated their support for a peaceful resolution of the disputes, which some fear could spark Asia’s next conflict.

“They should develop a code of conduct,” U.S. Ambassador Harry Thomas Jr. told foreign correspondents in a news forum. “This was agreed to in 2002 and it should be expanded.”

Asked if a new Spratlys accord should be legally binding, Thomas replied: “Of course.”

He did not specify any feature Washington wanted to see in a new Spratlys accord but added that if asked, the United States would be willing to extend help to ASEAN during negotiations for a new agreement — something that Beijing would likely resist.

The Chinese Embassy reiterated Monday that the disputes “should be resolved only between China and claimant countries.”

A new code of conduct in the disputed region should “ensure regional stability and freedom of navigation for international commerce,” Thomas said.

Responding to another question, Thomas said it was not up to Washington whether claimants should be required to disarm or demobilize forces stationed in the contested region under a new pact.

The disputed territories include the Spratlys, claimed in whole or in part by four ASEAN members — Malaysia, the Philippines, Brunei and Vietnam — plus China and Taiwan. Also contested are Scarborough Shoal, claimed by the Philippines and China, and the Paracel Islands, disputed by China and Vietnam.

Although largely uninhabited, the areas are believed to be sitting atop vast reserves of oil and natural gas. They straddle busy sea lanes and are rich fishing grounds.

Chinese Ambassador Liu Jianchao last week said that China and the other claimants have begun discussions to forge a stronger code of conduct over the Spratlys.

“The document is still in the process of being negotiated,” Liu told reporters.

“We are open to different formulas and initiative in preserving peace, prosperity and stability in this region,” Liu said, without elaborating.

China and ASEAN members have not specified how they want the 2002 accord to be strengthened or how provisions under a new code of conduct can be made legally enforceable.

Beijing angrily reacted after U.S. Secretary of State Hillary Clinton told an ASEAN regional security forum in Vietnam in July that the peaceful resolution of disputes over the Spratly and Paracel island groups was in the American national interest.

Beijing said Washington was interfering in an Asian regional issue.

The conflicting claims have occasionally erupted into armed confrontation. Chinese forces seized the western Paracel Islands from Vietnam in 1974 and sank three Vietnamese naval vessels in a 1988 sea battle.