ASEAN secretary-general Surin Pitsuwan (centre) takes part in an ASEAN meeting yesterday at the Peace Palace in Phnom Penh. Photograph: Hong Menea/Phnom Penh Post

A UN maritime convention that puts limits on claims in disputes over territorial waters should be the basis for negotiations over the South China Sea, ASEAN foreign ministers agreed in a draft document signed yesterday.

China is locked in a dispute over the South China Sea with several countries attending this week’s ASEAN Regional Forum in Phnom Penh, but has nevertheless yielded influence in drafting an ASEAN Code of Conduct on the issue.

The burgeoning superpower is unlikely to be thrilled by moves to make the UN Convention on the Law of the Sea the basis of negotiations, which it is a signatory to but which would likely conflict with its claim to almost all of the disputed waters.

“UNCLOS has been there all along, even in the declaration back in 2002 here. UNCLOS is one of the pillars of international negotiations, international relations,” outgoing ASEAN Secretary-General Surin Pitsuwan said on the sidelines of the forum yesterday.

Pitsuwan said in formulating the COC, ASEAN was taking norms adopted from the outside world and transferring them to the regional context.

“We are not inventing the wheel, but at the same time, by putting them together as our own body of rules and regulations and norms, we are making it, I think, more credible and more legitimate,” he said.

Taiwan and ASEAN members the Philippines, Vietnam, Brunei and Malaysia all make rival claims on areas of the sea.

Cambodia has traditionally supported China’s claim over the waters, but government officials were tight-lipped about the issue yesterday.

“You only focus on the South China Sea. Why don’t you focus also on the co-operation? On the many important issues?” Foreign Affairs secretary of state Seung Rathchavy asked reporters.

When quizzed about the South China Sea after giving a vague and rapid press briefing, Foreign Ministry secretary of state Kao Kim Hourn gave a brusque answer and abruptly marched out of a press briefing.

“Very briefly, one of the ministers just touched on the need to . . . work toward the COC. That’s all that was talked about, very briefly,” he said before leaving.

He promptly returned after realising he had left without giving the Khmer-language version of the briefing.

With assistance from David Boyle