The language was more moderate than that of an earlier draft of the joint statement which opposed the 'use or threat of force by any claimant attempting to enforce disputed claims in the South China Sea'. Hours after the meeting, Foreign Ministry spokeswoman Jiang Yu said in Beijing: 'China has and always will work for the peaceful resolution of South China Sea disputes.'

She said China hoped the states concerned would deal with the disputes in the same spirit as China and promoted good-neighbourly relations and mutual trust in the region to ensure its peace and stability.

Chinese envoys had lobbied Asean members ahead of the summit, several diplomats said. Asean operates on consensus decision-making - meaning smaller, less powerful members are often considered vulnerable to outside pressure to change an outcome.

China has been increasingly strident about its claims to sovereignty over two island chains, the Spratlys and Paracels. Asean member Vietnam claims sovereignty over all the islands, and the Philippines, Malaysia and Brunei claim of them. Beijing this year designated the South China Sea a 'core interest' of China, putting it on a par with Tibet and Taiwan.

Chinese envoys have told international oil giants - including ExxonMobil and BP - to pull out of deals with Vietnam to prospect for oil in the South China Sea with Vietnam or face commercial punishment.

This posturing has worried China's neighbours - notably Vietnam, whose fishermen China frequently detains near the disputed areas.

The regional bloc's leaders welcomed American involvement in the issue, said Amitav Acharya, who chairs the Asean studies programme at the American University in Washington. 'Asean sees the US as a kind of countervailing force at a time when China seems to be more assertive in the South China Sea,' Acharya said.

The US has signalled that it is happy to take on that role, seeing it as an opportunity to keep promises to re-engage the region meaningfully. In July, Secretary of State Hillary Rodham Clinton infuriated Beijing by telling Asean leaders at a forum in Hanoi that access in the South China Sea and a peaceful, multilateral solution to the territorial disputes there were a US diplomatic priority.

The US conducts naval exercises in the South China Sea, which links the oil- and trade-dependent economies of China, Japan and South Korea to the Middle East and Europe.

'We converge on the idea that the Chinese claims are just absurd,' said Walter Lohman, director of the Asian Studies Centre at the hawkish Heritage Foundation in Washington.

Threats that China's growing naval strength could add teeth to its stated claims have created urgency for its regional neighbours as well as the US. Still, said Lohman, not all of Asean's leaders would necessarily relish a chance to confront their neighbour head-on over the issue, which may account for the softer language in the final joint statement.

The tussle over the South China Sea - and the US role in it - is likely to continue. Jeff Bader, the senior director for Asian affairs in the US National Security council, said on Thursday that Premier Wen Jiabao and Obama discussed the issue briefly when they met in New York, with Obama reiterating Clinton's earlier remarks.

Obama and the Asean leaders emphasised the importance of trade and investment between the US and Southeast Asia. They also discussed climate change, security issues and human rights violations in Myanmar, according to a US statement.

'As president, I've ... made it clear that the United States intends to play a leadership role in Asia,' said Obama before the meeting. 'So we've strengthened old alliances; we've deepened new partnerships, as we are doing with China; and we've re-engaged with regional organisations, including Asean.'