China offered an olive branch Wednesday to Southeast Asian nations wary of Beijing's territorial claims, keeping its growing clout on display at yet another summit notable by US President Barack Obama's absence.

Premier Li Keqiang called for a South China Sea of "peace and friendship", during a meeting with the heads of the 10-member Association of Southeast Asian Nations (ASEAN) in the oil-flush sultanate of Brunei.

"A peaceful South China Sea is a blessing for all. We need to work together to make the South China Sea a sea of peace, friendship and cooperation," Li said.

Li took the baton from President Xi Jinping, who underlined Chinese power by occupying centre-stage in previous days at an Asia-Pacific summit in Bali with Obama stuck at home due to the US government shutdown.

Some ASEAN members who hold various claims to the South China Sea have voiced increasing alarm at perceived provocative acts by Beijing in asserting its claims in the strategic body of water.

China has sought to portray a friendlier face more recently, dangling lucrative trade promises around the region -- while holding its ground on its claims to most of the South China Sea.

In sharp contrast to the often icy tone China takes with perceived rivals like the United States and Japan, Li showered his ASEAN counterparts with pledges of friendship and deeper economic integration.

Smiling and energetic, he called for the two sides to ramp up efforts to more than double China-ASEAN trade to $1 trillion by 2020, from about $400 billion last year.

Obama had said earlier in the year he planned during the Brunei gathering to lend his presidential prestige to calls for a speedy agreement between China and ASEAN on a code of conduct at sea to avoid accidental conflict.

However, as he did in Bali, Obama's top diplomat John Kerry was in Brunei instead to show support for America's Asian allies.

The two days of revolving-door talks in Brunei include ASEAN, the United States, Japan, and South Korea and several other regional players.

China has succeeded in lowering temperatures by agreeing recently to join with ASEAN in initial talks toward a code of conduct.

Even the Philippines -- usually one of the most vociferous critics of Beijing's claims in the South China Sea -- welcomed the tentative signs of a thaw.

"In recent months discussions on the code of conduct between China and ASEAN have met with some degree of progress," President Benigno Aquino's spokesman Ramon Carandang told reporters in Brunei.

"Right now you're seeing everybody engaging, even China."

Li and the Southeast Asian leaders were all smiles as they cut a giant blue and pink cake to mark the 10th anniversary of a China-ASEAN strategic partnership.

However, some experts view Beijing's recent moves as a bid to buy time while it continues to build its regional clout.

"(China) is not going to compromise on its claims," said Ian Storey of the Institute of Southeast Asian Studies in Singapore.

China signalled ahead of the meetings that it would not look kindly on attempts to raise sea disputes at an expanded East Asia Summit of 18 nations on Thursday, in comments that appeared aimed at Washington.

The South China Sea, which is believed to sit atop vast deposits of oil and natural gas, has long been regarded as a potential military flashpoint.

The Philippines, Vietnam, Malaysia and Brunei -- all members of ASEAN -- also have various claims to the strategic sea.

Territorial tensions between Japan and neighbouring China and South Korea have also soared in recent years.

The three countries each held separate bilateral talks with the ASEAN bloc on Wednesday. A group gathering between ASEAN and the three East Asian powers was planned for Thursday.

However, reflecting deep-seated mistrust over maritime disputes, Beijing has ruled out bilateral talks between Li and Japanese Prime Minister Shinzo Abe in Brunei.

With the region facing increasing economic headwinds, trade was high on the agenda at the Brunei talks.

ASEAN, a vibrant region of 600 million people, wants to establish a common market and manufacturing base to better compete with economic powers China and India, but there are growing doubts about whether it will meet its 2015 target.

"With two years left to go we still face challenges in implementing our community roadmap," Brunei's ruler, Sultan Hassanal Bolkiah, told his counterparts during an annual ASEAN summit in the morning.

ASEAN is also pushing an ambitious 16-nation free trade zone called the Regional Comprehensive Economic Partnership, which also involves Australia, China, India, Japan, South Korea and New Zealand.

The initiative is seen as rivalling the Trans-Pacific Partnership, a 12-nation trade pact championed by Washington.