CANBERRA (AFP) ― U.S. President Barack Obama arrived in Australia Wednesday on a twice-postponed mission to update a 60-year-old security alliance for a new century marked by the rise of China.

Air Force One touched down in the capital Canberra after flying from the president’s native Hawaii, where he presided over a summit that expanded entry talks on a new pan-Pacific trade deal.

The 28-hour visit to Australia is expected to include an announcement on escalating military cooperation, in a clear statement by Washington that it intends to stand up for its interests and allies in a fast-emerging region.

Obama, who is seeking to reorient security policy towards Asia as the United States transitions out of Iraq and Afghanistan, wants to stress important economic and strategic ties between Australia and the United States.

The new arrangements “will speak to the deepening cooperation between the United States and Australia”, Deputy National Security Advisor Ben Rhodes said on Air Force One.

“It’s in response to Australia’s interest in pursuing that cooperation, and it will enable the U.S. to have greater geographic balance in the Asia-Pacific region, it will enable us to respond to a range of interests in the Pacific region as well.”

The U.S. leader is set to hold talks with Prime Minister Julia Gillard later Wednesday and take part in a joint press conference, before addressing parliament on Thursday in what aides said is the “anchor speech” of his tour.

When George W. Bush addressed the Canberra parliament in 2003, Australian Greens leader Bob Brown heckled the president about the U.S.-led war in Iraq.

Brown is expected to be in the chamber when Obama speaks.

After Australia, Obama heads to Indonesia to attend Saturday’s East Asia Summit, a 16-nation grouping including China that the United States and Russia are joining for the first time.

Canberra has gone into virtual lockdown for the visit with hundreds of U.S. Secret Service agents helping with security arrangements that have seen roads closed, F/A 18 Hornet fighter jets patrolling overhead and snipers on rooftops.

On Thursday, Obama heads to Darwin, where he is expected to announce U.S. Marines will be deployed to an existing Australian base near the northern city.

Washington appears to be sending a signal to China and its expanding military with its deployment in Australia, but the White House also wants to extend its capability to deploy for disaster relief missions in Southeast Asia.

“There’s a range of factors that leads us to want to increase our cooperation with Australia, and ensure that we have an appropriate military posture in the Asia-Pacific,” Rhodes said.

Gillard insisted that strengthening the U.S.-Australia alliance was not a threat to a rising China, whose voracious demand for Australia’s natural resources has made it the nation’s biggest trading partner.

“I think it is well and truly possible for us, in this growing region of the world, to have an ally in the United States and to have deep friendships in our region, including with China,” she said.

U.S. and Australian forces have served shoulder-to-shoulder in World War II, Korea, Vietnam and the wars in Iraq and Afghanistan, and U.S. intelligence services retain a secret listening post at Pine Gap in the Australian outback.

Obama, who is facing a tough reelection campaign next year amid high unemployment and economic gloom, has twice been forced to postpone plans to visit Australia because of domestic political crises.

But in an attempt to synch domestic imperatives with foreign policy, aides are billing Obama’s Pacific tour as an attempt to pry open the regional markets that will be crucial to America’s economic future.

Obama is also hugely popular in Australia and is assured a warm welcome that may provide some relief to a president whose image has been battered by three brutal years in a deeply partisan Washington.