Southeast Asian foreign ministers Monday said they were ready to open talks with Beijing over easing friction in the South China Sea, after agreeing key points of a pact aimed at preventing maritime disputes.

Cambodian Prime Minister Hun Sen said hammering out a code of conduct with China was a chief goal for the 10-member Association of Southeast Asian Nations (ASEAN), at the beginning of annual talks in Phnom Penh.

Tension over competing claims in the South China Sea promises to be the hot button issue of the meetings, particularly later in the week when US Secretary of State Hillary Clinton and her Chinese counterpart are among regional participants for the security-focused ASEAN Regional Forum (ARF).

As the first day of talks concluded, Kao Kim Hourn, secretary of state at the Cambodian foreign ministry, told reporters that foreign ministers had adopted "key elements" of the proposed code of conduct to govern behaviour between nations involved in disputes.

"Foreign ministers have agreed to have the ASEAN senior officials meet with the senior official from China to discuss the (code of conduct) from now on," said Kao Kim Hourn, whose country holds the rotating chairmanship of the bloc.

China claims essentially all of the South China Sea, home to vital shipping lanes and believed to be rich in oil and gas deposits. Taiwan and ASEAN members the Philippines, Vietnam, Brunei and Malaysia also have claims in the waters.

Regional tensions have risen recently, with both Vietnam and the Philippines accusing Beijing of aggressive behaviour in the South China Sea.

China on Monday said it was willing to discuss the issue with ASEAN "when conditions are ripe" but insisted that any potential pact must not be used to resolve rival claims.

"The (code of conduct) is not aimed at resolving disputes, but aimed at building mutual trust and deepening cooperation," China's foreign ministry spokesman Liu Weimin told journalists in Beijing.

While that stance may put China at odds with some ASEAN members, it is consistent with Beijing's desire to settle disputes with claimants bilaterally.

"It's expected that China would work with ASEAN. It's the only way to get the US off their back," said Carl Thayer, a politics professor and Southeast Asia security expert at the University of New South Wales in Australia.

"But what is ASEAN proposing and how will China react? We don't know whether the proposed code will have a dispute settlement mechanism," he added.

Strategic rivalry between Washington and Beijing is expected to loom large over the summit, following the recent expansion of US military relations with the Philippines and Vietnam.

Clinton has previously said the US has a "national interest" in open access to the sea, but observers predict a softer stance this week, with Washington likely to downplay friction with China.

ASEAN is hoping to get an agreement with China on the code by the end of the year and the group's secretary general Surin Pitsuwan told reporters that ASEAN wanted to show the world it could make progress on the maritime dispute.

"We will engage in a rational, effective discussion on the issue with all the parties," he said.

China recently angered Vietnam by inviting bids for exploration of oil blocks in contested waters, sparking protests in Hanoi, while Manila and Beijing are locked in a standoff over a disputed shoal.

ASEAN comprises Brunei, Cambodia, Indonesia, Laos, Malaysia, Myanmar, the Philippines, Singapore, Thailand and Vietnam -- a grouping of nearly 600 million people from disparate economic and political systems.

The bloc, often dismissed as a talking shop in the past, has assumed new strategic importance in light of Washington's foreign policy "pivot" to Asia and the economic rise of China in recent years.