Tensions between the United States and China threaten to spill over into meetings of Asia-Pacific leaders from Friday, with President Barack Obama declaring his intention on the eve of the gathering to assert U.S. influence in the region.

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

And 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 pushed for a new Asia-Pacific trade deal with some of Beijing's neighbours.

The Indonesia meetings, on the resort island of Bali, bring together the 10-member Association of South-East Asian Nations (ASEAN) and eight dialogue partners, including the United States, China, Russia and Japan. Bilateral meetings are held on Friday before a full East Asia summit Saturday.

Earlier this week, U.S. Secretary of State Hillary Clinton urged claimants to the South China Sea not to resort to intimidation to push their cause in the potentially rich waters, an indirect reference to China ahead of the Bali summit.

China and several ASEAN countries have clashed over sovereignty of the waters, believed to be rich in natural resources and straddling vital trade lanes.

Clinton called for candid discussion of the maritime dispute at the summit, which could embolden some Southeast Asian countries with maritime claims, though China says it does not want such talks to take place and that the issue should be resolved via bilateral negotiations.

Introducing a contentious subject into the meeting would only affect the atmosphere of cooperation and mutual trust, damaging the hard-won setting of healthy development in the region, Chinese Foreign Ministry spokesman Liu Weimin said on Wednesday. That's is beyond any doubt.

Obama has declared that U.S. engagement in the Asia-Pacific region was absolutely critical, feeding China's longstanding fears of being encircled by the United States and its allies.

As we end today's wars, I have directed my national security team to make our presence and missions in the Asia Pacific a top priority, Obama said Thursday in a major speech on Washington's vision for the Asia-Pacific region.

As a result, reductions in U.S. defence spending will not -- I repeat, will not -- come at the expense of the Asia Pacific.

Nervous about China's growing clout, U.S. allies such as Japan and South Korea have sought assurances from the United States that it would be a strong counterweight in the region.

A first step in extending the U.S. military reach into Southeast Asia will see U.S. Marines, naval ships and aircraft deployed to northern Australia from 2012.

That deployment to Australia, which by 2016 will reach a taskforce of 2,500 U.S. troops, is small compared with the 28,000 troops stationed in South Korea and 50,000 in Japan.

But the presence in Darwin, only 820 km (500 miles) from Indonesia, will allow the United States to quickly reach into Southeast Asia and the Indian Ocean.

Obama acknowledged China's unease at what it sees as attempts by Washington to encircle it, pledging to seek greater cooperation with Beijing.

He added: We'll seek more opportunities for cooperation with Beijing, including greater communication between our militaries to promote understanding and avoid miscalculation.

The new de facto U.S. base in Australia expands the direct U.S. military presence in Asia beyond South Korea and Japan and into Southeast Asia, an area where China has growing economic and strategic interests.

It will also put more U.S. troops, ships and aircraft much closer to the South China Sea.

CHINA QUESTIONS U.S. DEPLOYMENT TO AUSTRALIA

China has questioned the new U.S. deployment, with a foreign ministry spokesman raising doubts about whether strengthening such alliances helped the region pull together at a time of economic gloom.

But overall its official reaction has been restrained, with an impending leadership succession preoccupying the ruling Communist Party and leaving Beijing anxious to avoid diplomatic fireworks.

Reaction from some state media was harsher.

It wouldn't come as a surprise if the United States is trying to seek hegemony in the region, which would be in line with its aspirations as a global superpower, China's state news agency Xinhua said in a commentary.

Obama said the increased focus on the Asia-Pacific region was essential for America's economic future.

As the world's fastest-growing region - and home to more than half the global economy - the Asia Pacific is critical to achieving my highest priority: creating jobs and opportunity for the American people, he said.

(Additional reporting by Michael Perry in Sydney; writing by Neil Fullick; editing by Mark Bendeich)