Southeast Asian leaders feuded on Monday over how to handle tense maritime territorial disputes with China, overshadowing talks at a regional summit meant to strengthen trade and political ties.

The leaders of the 10-member Association of Southeast Asian Nations had hoped to present a united front on the South China Sea row as they host Chinese Premier Wen Jiabao and US President Barack Obama for annual talks.

But that effort broke down just before Southeast Asian leaders were scheduled to meet Wen, amid divisions between Chinese ally Cambodia and the Philippines.

Cambodia, this year's ASEAN chair, said on Sunday that Southeast Asian leaders had agreed not to "internationalise" the disputes and would confine negotiations to those between the bloc and China.

The apparent deal would have been a victory for China, which has long insisted that it should only negotiate directly with rival countries and that the Philippines should not seek support from the United States.

However Philippine President Benigno Aquino on Monday publicly rebuked Cambodian Prime Minister Hun Sen, telling his fellow leaders no such consensus had been reached and he would continue to speak out on the global stage.

"The Philippines... has the inherent right to defend its national interests when deemed necessary," Philippine Foreign Secretary Albert del Rosario told reporters, quoting Aquino's comments to his fellow leaders on Monday morning.

The feud echoed unprecedented infighting at an ASEAN foreign ministers' meeting in Phnom Penh in July, which ended for the first time in the bloc's 45-year history without a joint communique.

The Philippines and Vietnam had wanted the communique to make specific reference to their disputes with China. But Cambodia, the hosts of the talks and a close China ally, blocked the moves.

ASEAN members Vietnam, the Philippines, Malaysia and Brunei, as well as Taiwan, have claims to parts of the sea, which is home to some of the world's most important shipping lanes and believed to be rich in fossil fuels.

But China insists it has sovereign rights to virtually all of the sea.

Tensions have risen steadily over the past two years, with the Philippines and Vietnam accusing China of increasingly aggressive diplomatic tactics to stake its claims.

Temperatures could rise again later Monday when Obama arrives in Phnom Penh to join the East Asia Summit, a two-day event also involving the leaders of Japan, South Korea, India, New Zealand and Australia.

Obama has previously angered China, and emboldened the Philippines, by calling for the rival claimants to agree on a legally binding code of conduct to govern their actions over the sea.

Analysts said he would likely repeat that call in Phnom Penh, as well as make comments highlighting the importance of freedom of navigation in the sea.

ASEAN officials had said they would push Wen during their talks on Monday to quickly start high-level, formal negotiations on a code of conduct.

But Chinese foreign ministry spokesman Qin Gang insisted that China wanted to continue with the current arrangement of lower-level talks on the issue. "We already have good discussions with ASEAN," Qin said.

Even with the South China Sea row festering, countries involved in the East Asia Summit were expected to focus on ways to expand economic ties.

ASEAN nations are set to officially launch negotiations on Tuesday for an enormous free trade pact with China, Japan, India, South Korea, Australia and New Zealand.

And despite their own territorial rows, China, Japan and South Korea are likely to hold talks in Phnom Penh on Tuesday aimed at kickstarting three-way free trade negotiations, according to Qin.