Vowing to deepen ties with the strategic Asia-Pacific region using "every element of American power", Obama said that America has an "iron-clad commitment to the sovereignty, independence, and security of every ally."

"And we'll expand cooperation between allies, because we believe we're stronger when we stand together," he said, underlining that the security in Asia must depend on mutual alliances.

"We believe that nations and peoples have the right to live in security and peace; that an effective security order for Asia must be based - not on spheres of influence, or coercion, or intimidation where big nations bully the small - but on alliances of mutual security, international law and international norms that are upheld, and the peaceful resolution of disputes," Obama said on Saturday while addressing students at the University of Queensland.

Warning that territorial disputes could spiral into confrontation, he said America had an iron clad commitment to the sovereignty of its allies.

"Any effective security order for Asia must be based not on spheres of influence, or coercion or intimidation where big nations bully the small but on alliances for mutual security, international law and norms that are upheld, and the peaceful resolution of disputes," Obama said.

Though he did not mention China explicitly in his speech, he warned of the dangers posed by territorial disputes in the resource-rich South China Sea, where Beijing's actions have raised concern among its neighbours, including the Philippines and Vietnam.

He praised Asean's effort to reach a code of conduct with China that reinforces international law in the disputed South China Sea.

Obama said that American leadership in the Asia Pacific will always be a fundamental focus of his foreign policy.

"It won't always make the headlines. It won't always be measured in the number of trips I make - although I do keep coming back. But day in, and day out, steadily, deliberately, we will continue to deepen our engagement using every element of American power - diplomacy, military, economic, development, the power of our values and our ideals," he said.

He said the US will continue strengthening its alliances. "With Japan, we'll finalise new defense guidelines and keep realigning our forces for the future. With the Republic of Korea, we'll deepen our collaboration, including on missile defence, to deter and defend against North Korean threats.

"With the Philippines, we'll train and exercise more to prepare for challenges from counterterrorism and piracy to humanitarian crises and disaster relief. And here in Australia, more US Marines will rotate through to promote regional stability...," Obama said.

China, wary of Obama's proposed "pivot to Asia" strategy, has long viewed suspiciously the trilateral relationship between the US, Australia and Japan, which it sees as an attempt to counter Beijing's growing influence.

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