President Barack Obama announced on Thursday that the U.S. military would expand its role in the Asia-Pacific region, despite budget cuts, declaring America was here to stay as a Pacific power which would help shape the region's future.

China has voiced misgivings about Obama's announcement of fresh troop deployments to Australia and has longstanding fears that its growing power could be hobbled by U.S. influence. But Beijing has also stressed that conflict is in nobody's interest.

Obama addressed the Chinese unease, pledging to seek greater cooperation with Beijing.

The U.S. military, turning its focus away from Iraq and Afghanistan, would be more broadly distributed in Asia, particularly Southeast Asia, more flexible and help build regional capacity, Obama told the Australian parliament.

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 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.

Obama was clear in acknowledging China's discomfort at what it sees as attempts by Washington to encircle it.

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

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.

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

Obama said the United States would seek to work with China to ensure economic prosperity and security in the region, but would speak candidly about issues such as human rights in China and raise security issue like the South China Sea.

China claims the South China Sea, a vital shipping route rich in oil, minerals and fishery resources. But Vietnam, the Philippines, Taiwan, Malaysia and Brunei hold rivals claims to at least parts of the sea, sparking maritime stand-offs.

U.S. Secretary of State Hillary Clinton pointedly visited the Philippines on Wednesday, saying that no claimant should resort to intimidation to push its cause.

Obama also referred in his address to reforms undertaken by Myanmar's new civilian leaders, including the release of political prisoners. But he said they had to do more on human rights in order to secure better relations with Washington.

Rory Medcalf, security analyst at the Lowy Institute for International Policy in Sydney, said Obama's speech marked a hardening of policy towards China, though he noted that the president was still reaching out to Beijing.

I think we are seeing a firm stance from Obama. He spent the first year of his presidency trying very hard to engage with China, perhaps even to accommodate China, said Medcalf.

I think he feels that he was rebuffed and that he was in effect taken advantage by China. So, there is a fundamental reorienting of American policy on display here.

U.S. SEEKS MORE FLEXIBLE FORCES IN ASIA

The winding down of wars in Afghanistan and Iraq has opened the door to greater U.S. attention to simmering tension over the South China Sea, a shipping lane for more than $5 trillion (3.2 trillion pounds) in annual trade that the United States wants to keep open.

Obama and Australian Prime Minister Julia Gillard on Wednesday agreed to have 2,500 U.S. Marines operate out of a de facto base in the northern port of Darwin by 2016.

The United States has military bases and large forces in Japan and South Korea, but its presence in Southeast Asia was dramatically reduced in the early 1990s with the closure of bases at Clark Field and Subic Bay in the Philippines.

Deploying U.S. Marines, ships and aircraft in Darwin, only 820 km (500 miles) from Indonesia, will allow the United States to quickly reach into Southeast Asia and the Indian Ocean to ensure secure major trade sea-lanes.

Obama cited increased U.S. naval ship visits and training in the Philippines and Singapore, working with Indonesia to fight piracy, partnering Thailand for disaster relief, and significantly, acknowledged India's role in region security.

Washington welcomed India as it 'looks east' and plays a larger role as an Asian power.

We'll have new opportunities to train with other allies and partners, from the Pacific to the Indian Ocean, he said.

Medcalf said: It will be a landmark speech of Obama's presidency. It states unequivocally that the U.S. is squarely focussing its strategic attention on Asia. Its defining that Asia as including the Indian Ocean and India.

In a note to his domestic audience, Obama said the increased focus on Asia-Pacific 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.

Obama will fly to Bali late on Thursday, where he will seek to underscore a focus on Asia by becoming the first U.S. president to participate in the security East Asia Summit.

(Writing by Michael Perry; Editing by Lincoln Feast and Ron Popeski)