US President Barack Obama has succeeded in hauling a maritime dispute into an Asian summit despite China's objections, in a diplomatic victory at the end of his Pacific tour.

The "robust" discussion on the South China Sea territorial row, at the East Asia Summit on the Indonesian resort island of Bali, took place after a week of increasingly sharp exchanges between the two world powers.

Washington's new diplomatic campaign to assert itself as a Pacific power has alarmed China which sees the initiatives as intruding into its sphere of influence.

China's Premier Wen Jiabao has warned against interference by "external forces" in the wrangle, over a strategic and resource-rich area where several regional nations have overlapping claims.

However, shortly after hastily arranged talks between Mr Obama and Mr Wen on the summit sidelines, the group leaders held a "very robust conversation on maritime security and the South China Sea," according to a US administration official.

Mr Obama was "encouraged" by the talks and the tone was "constructive," the official said on condition of anonymity.

Chinese state media indicated that Mr Wen reluctantly agreed to the issue being raised at the 18-nation summit.

"I don't want to discuss this issue at the summit, however, leaders of some countries mentioned China on the issue. It's impolite not to make a return for what one receives," he said according to the official Xinhua news agency.

"The South China Sea is an important transportation passageway for China, regional countries and even the world. The Chinese government has made a positive contribution to safeguard the navigation security in the South China Sea," he added.

China, which claims the South China Sea in full, had insisted on discussing the dispute individually with its smaller neighbours but the US has now succeeded in making it a topic for debate at an international forum.

The region is a conduit for more than one-third of the world's seaborne trade and half its traffic in oil and gas, and major petroleum deposits are believed to lie below the seabed.

China claims all of it, as does Taiwan, while four Southeast Asian countries declare ownership of parts of it, with Vietnam and the Philippines accusing Chinese forces of increasing aggression there.