The United States and China are set to face off on Saturday at a regional summit over the thorny issue of how to resolve competing claims to sovereignty of the South China Sea, the latest point of friction between the two powerful nations.

Chinese Premier Wen Jiabao insisted on Friday that outside forces had no excuse to get involved in the complex maritime dispute, a veiled warning to the United States and other countries to keep out of the sensitive issue.

Vietnam, the Philippines, Taiwan, Malaysia and Brunei all have claims to parts of the South China Sea, a major route for some $5 trillion in trade each year and potentially rich in resources. China claims large parts of the maritime region.

The Southeast Asian countries along with the United States and Japan are pressuring Beijing to try to seek some way forward on the knotty issue of sovereignty, which flared up again this year with often tense maritime stand-offs that an Australian think tank said could lead to conflict.

China wants to hold bilateral talks with other countries that claims parts of the South China Sea as their territory, but the Southeast Asian claimants, the United States and Japan are pushing for a multilateral approach.

It ought to be resolved through friendly consultations and discussions by countries directly involved. Outside forces should not, under any pretext, get involved, Wen told a meeting with Southeast Asian leaders on Friday, several of whose countries claim sovereignty to parts of the South China Sea.

Wen's comments were carried on the Chinese Foreign Ministry's website (www.mfa.gov.cn).

Obama has been more low key as far as public comments are concerned. He told the leaders of India, the Philippines, Indonesia and Malaysia in bilateral meetings that the East Asia Summit, which draws together Southeast Asian nations and eight dialogue partners, was the right arena to discuss maritime disputes.

U.S. Deputy National Security adviser for strategic communications, Ben Rhodes, said earlier this week that in the discussion about maritime security, the South China Sea will clearly be a concern.

Obama and Wen plan to meet on the sidelines of the summit before the leaders start their formal meeting.

INFLUENCE

Their exchanges are the latest barbs between the two countries in recent weeks as Obama has sought to reassert U.S. presence in the Asia-Pacific to counter the growing clout of the world's second-largest economy, China.

Obama said in Australia on Thursday, on his last stop before jetting to the Asia meetings in neighbouring Indonesia, that the U.S. military would expand its Asia-Pacific role, declaring America was here to stay as a Pacific power.

Days earlier, as host of the Asia Pacific Economic Co-Operation forum in Hawaii, Obama had voiced growing frustration at China's trade practices and he pushed for a new Asia-Pacific trade deal with some of Beijing's neighbours.

The moves are seen as an attempt to reassert U.S. leadership in the face of China's rising influence around the Pacific Rim and reassure allies such as South Korea and Japan that it would remain a strong counterweight.

Obama also announced on Friday that he would send Secretary of States Hillary Clinton next month to Myanmar, which has drawn closer to China in reaction to Western sanctions, the first such trip to the isolated country in half a century.

That will add to some fears in Beijing of encirclement in the Asia Pacific as the United States increases its footprint in the region.

CLAIMS

China's claims over the South China Sea is by far the largest, forming a U-shape over most of the sea's 648,000 square miles (1.7 million square kms), including the Spratly and Paracel archipelagos.

The United States has irked China by declaring a national interest at stake in the South China Sea by ensuring the freedom of navigation and trade.

Estimates of proven and undiscovered oil reserves in the South China Sea range from 28 billion barrels of oil to as high as 213 billion barrels, U.S. figures showed in 2008. Gas deposits could be as high as 3.8 trillion cubic metres.

Both could supply China with energy for decades.

The Philippines has called for greater unity among Southeast Asian nations with claims in their stand against China. A strong position from the United States in support of open talks could embolden such unity.

(Writing by Neil Fullick)