Festering territorial disputes provide the backdrop for an Asian summit kicking off Wednesday with China flexing its diplomatic muscle in the absence of a grounded President Barack Obama.
China and its Southeast Asian neighbours will attempt to overcome maritime tensions and inject fresh momentum into regional free-trade initiatives at two days of meetings in the oil-rich sultanate of Brunei.
The talks -- which include Southeast Asian nations, China, Japan, South Korea and the United States -- come on the heels of an Asia-Pacific summit in Bali overshadowed by Obama's no-show.
The US president was forced to skip the back-to-back meetings because of deepening political deadlock in Washington that has left his so-called diplomatic "pivot" towards Asia in doubt.
On Tuesday Obama insisted his absence would not hurt the US role in Asia, saying he expected no "lasting damage", but admitted China may have been happy he cancelled.
It is now up to his top diplomat John Kerry to show Washington's support for its Asian allies in the face of Beijing's uncompromising territorial claims to areas including most of the South China Sea.
The Philippines, Vietnam, Malaysia and Brunei -- all members of the 10-nation Association of Southeast Asian Nations (ASEAN) -- also consider parts of the strategically vital waters as their territory.
But the bloc has struggled to present a united front on the issue with Cambodia -- a key ally of China -- resisting attempts to take Beijing to task when it held the ASEAN chair last year.
China signalled ahead of the meetings that it would not look kindly on attempts to raise the issue at an expanded East Asia Summit of 18 nations on Thursday, including ASEAN, the United States, and Russia, in comments seen as aimed at the United States.
"Involvement by foreign countries... usually involves their own agenda and it will not help build consensus or shore up mutual trust between countries in this region," China's Vice Foreign Minister Liu Zhenmin said on Monday.
Obama had said earlier in the year he planned during the meeting to lend his presidential prestige to the US push for a speedy agreement between China and ASEAN on a Code of Conduct at sea to avoid accidental conflict.
He will instead be represented by US Secretary of State Kerry, while Premier Li Keqiang will head China's delegation.
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.
Beijing has succeeded in lowering temperatures by agreeing to join with ASEAN in initial consultations on a code of conduct, but many experts, view that as a bid to buy time while quietly building its regional diplomatic, economic and military clout.
"In the meantime, China is growing stronger militarily. It is expanding its civilian maritime agencies. It is not going to compromise on its claims," said Ian Storey of the Institute of Southeast Asian Studies in Singapore.
Territorial tensions between Japan and neighbouring China and South Korea have also soared in recent years.
Reflecting deep-seated mistrust over maritime disputes, Beijing ruled out bilateral talks between Chinese Premier Li Keqiang and Japanese Prime Minister Shinzo Abe in Brunei.
The Brunei talks will kick off Wednesday with a meeting of Southeast Asian leaders who will attempt to make progress toward a single regional economic market.
ASEAN, a 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.
The bloc 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.