Canberra: President Barack Obama said on Thursday that the US 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.

Wider reach: Barack Obama. Photo: AP

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

The US military, turning its focus away from Iraq and Afghanistan, would be more broadly distributed in Asia, particularly South-East Asia, more flexible and help build regional capacity, he 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."

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

Nervous about China’s growing clout, US allies such as Japan and South Korea have sought assurances from the US that it would be a strong counterweight in the region. A first step in extending the US military reach into South-East Asia will see US 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 US troops, is small compared with the 28,000 troops stationed in South Korea and 50,000 in Japan. But the presence in Darwin, only 820km from Indonesia, will allow the US to quickly reach into Southeast Asia and the Indian Ocean.

“It was here in Darwin that our alliance was born during Australia’s ‘Pearl Harbor’," Obama, with his sleeves rolled up, told 2,000 Australian and US troops in the tropical port, where he stopped off en route to Indonesia.

More bombs were dropped on Darwin during a World War Two Japanese raid than in Hawaii, but Obama said US-Australian troops regrouped and went on to major Pacific victories.

“Here in Darwin and northern Australia we will write the next proud chapter in our alliance," said Obama, adding US and Australian forces would ensure security of the Asian sea lanes to the north which were critical for both economies. The new de facto US base in Australia expands the direct US military presence in Asia beyond South Korea and Japan and into South-East Asia, an area where China has growing economic and strategic interests.

It will also put more US troops, ships and aircraft much closer to the South China Sea, over which Beijing has sovereignty disputes with several countries.

Obama will raise the issue of the South China Sea during the security East Asia Summit on the Indonesian island of Bali later this week.

China has questioned the new US 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, with a commentary from the official news agency Xinhua on Thursday saying that: “Every country in the region...has good reason to question the United States’ ambition".