Barack Obama, the US president, has called on China, Japan and other Asian nations to show restraint as a series of simmering maritime disputes threatens to upset peace and stability in the region.
Tensions in the South and East China Seas have escalated in the past two years as an increasingly assertive Beijing has clashed with Japan, the Philippines and Vietnam over waters that encompass vast oil and gas reserves, large fish stocks and key global trade routes.
More News From Financial Times
Stocks rebound as Obama starts budget talks
Stocks unsettled as Obama starts budget talks
Stocks stabilise as budget talks begin
Stocks advance on positive US data
Japan's stocks gain on election bets
"President Obama's message is there needs to be a reduction of the tensions in the East China Sea and a process going forward, more broadly, to ensure that these types of disputes don't risk escalation," said Ben Rhodes, a US deputy national security adviser. Speaking after the East Asia Summit, a meeting of regional leaders, on Tuesday in Phnom Penh, the Cambodian capital, he added that while the US was not a claimant, it had "significant interest there given its role in the global economy".
The EAS came at the end of a series of meetings organised by the Association of Southeast Asian Nations, where leaders were once again divided over how to respond to China as it enhances its naval power and becomes ever more strident in enforcing its extensive territorial claim in the South China Sea.
Cambodia, which is current chair of Asean and a key Beijing ally, clashed with the Philippines after mistakenly claiming that all member states had agreed not to raise the South China Sea disputes in international forums.
The president of the Philippines, which was dragged into a perilous maritime stand-off with Beijing earlier this year, told leaders including Wen Jiabao, China's premier, that there was an "urgent" need for countries to clarify their territorial claims in line with the UN law of the sea.
"At no time in the contemporary history of the South China Sea has clarification and delimitation of maritime areas become more urgent and imperative," said Benigno Aquino.
He echoed Mr Obama's call for meaningful talks between China and Asean about a code of conduct that would reduce tensions.
But China, which has long argued that maritime disputes should be discussed on a bilateral rather than international basis, remained defiant, blaming other countries for disturbing peace and stability in the region.
Qin Gang, a spokesman for China's foreign ministry, said that after a number of clashes with Japan over the disputed islands known as the Senkaku in Japan and Diaoyu in China, relations with Tokyo were "not good" but "the reason is not China's fault".
He also dismissed claims that Cambodia had been trying to damage south-east Asian unity to help strengthen China's position, suggesting that the Philippines and Vietnam were breaking the regional consensus because of their outspoken response to their disputes with China.