CANBERRA, Australia >> Signaling a determination to counter a rising China, President Barack Obama vowed Thursday to expand U.S. influence in the Asia-Pacific region and "project power and deter threats to peace" in that part of the world even as he reduces defense spending and winds down two wars.

"The United States is a Pacific power, and we are here to stay," he declared in a speech to the Australian Parliament, sending an unmistakable message to Beijing.

Obama’s bullish speech came several hours after announcing he would send military aircraft and up to 2,500 Marines to northern Australia for a training hub to help allies and protect American interests across Asia. He declared the U.S. is not afraid of China, by far the biggest and most powerful country in the region.

China immediately questioned the U.S. move and said it deserved further scrutiny.

Emphasizing that a U.S. presence in the Asia-Pacific region is a top priority of his administration, Obama stressed that any reductions in U.S. defense spending will not come at the expense of that goal.

"Let there be no doubt: in the Asia Pacific in the 21st century, the United States of America is all in," he said.

For Obama, Asia represents both a security challenge and an economic opportunity. Speaking in broad geopolitical terms, the president asserted: "With most of the world’s nuclear powers and some half of humanity, Asia will largely define whether the century ahead will be marked by conflict or cooperation, needless suffering or human progress."

Virtually everything Obama is doing on his nine-day trip across the Asia-Pacific region has a Chinese subtext, underscoring a relationship that is at once cooperative and marked by tensions over currency, human rights and military might.

China’s military spending has increased threefold since the 1990s to about $160 billion last year, and its military recently tested a new stealth jet fighter and launched its first aircraft carrier. A congressional advisory panel on Wednesday said China’s buildup is focused on dealing with America’s own defenses and exploiting possible weaknesses.

The panel, the U.S.-China Economic and Security Review Commission, urged the White House and Congress to look more closely at China’s military expansion and pressed for a tougher stance against what it called anticompetitive Chinese trade policies.

The U.S. and smaller Asian nations have grown increasingly concerned about China’s claims of dominion over Pacific waters and the revival of old territorial disputes, including confrontations over the South China Sea. China says it has sovereignty over the vast sea.

Responding to questions at a news conference Wednesday with Australian Prime Minister Julia Gillard, Obama said, "The notion that we fear China is mistaken."

While stressing his intent to increase influence in the Asia-Pacific region, Obama avoided a avoided a confrontational tone with China in his speech to the Australian parliament.

"We’ve seen that China can be a partner, from reducing tensions on the Korean Peninsula to preventing proliferation," he said. "We’ll seek more opportunities for cooperation with Beijing, including greater communication between our militaries to promote understanding and avoid miscalculation.

In a note of caution, however, he added: " We will do this, even as continue to speak candidly with Beijing about the importance of upholding international norms and respecting the universal human rights of the Chinese people."

China was immediately leery of the prospect of an expanded U.S. military presence in Australia. Foreign Ministry spokesman Liu Weimin said there should be discussion as to whether the plan was in line with the common interests of the international community.

With military bases and tens of thousands of troops in Japan and South Korea, the United States has maintained a significant military presence in Asia for decades. Australia lies about 5,500 miles south of China, and its northern shores would give the U.S. easier access to the South China Sea, a vital commercial route.

The plan outlined by Obama will allow the United States to keep a sustained force on Australian bases and position equipment and supplies there, giving the U.S. ability to train with allies in the region and respond more quickly to humanitarian or other crises.

About 250 U.S. Marines will begin a rotation in northern Australia starting next year, with a full force of 2,500 military personnel staffing up over the next several years. The United States will bear the cost of the deployment and the troops will be shifted from other deployments around the world. Having ruled out military reductions in Asia and the Pacific, the Obama administration has three main areas where it could cut troop strength: Europe, the Middle East and the U.S.

All U.S. troops are being withdrawn from Iraq by the end of this year, and a drawdown in Afghanistan is underway. But the Pentagon has said recently that the U.S. will maintain a major presence in the greater Middle East as a hedge against Iranian aggression and influence. A more likely area for troop reductions is Europe, although no decisions have been announced.

U.S. officials said the pact was not an attempt to create a permanent American military presence in Australia.

Australia’s Gillard said, "We are a region that is growing economically. But stability is important for economic growth, too." She said that "our alliance has been a bedrock of stability in our region."

Obama’s visit is intended to show the tightness of that relationship and he hailed the long ties between the United States and Australia, two nations far away that have spilled blood together

"From the trenches of the First World War to the mountains of Afghanistan_Aussies and Americans have stood together, fought together and given their lives together in every single major conflict of the past hundred years. Every single one," he said.

Obama had a packed day-and-a-half in Australia, his first trip here as president after canceling two previous tries. After addressing Parliament, Obama was flying to the northern city of Darwin, where some of the Marines deploying to Australia next year will be based.

In addition to the expanded Marine presence, more U.S. aircraft will rotate through Australia as part of an agreement between the nations’ air forces.

The only American base currently in the country is the joint Australia-U.S. intelligence and communications complex at Pine Gap in central Australia. But there are hundreds of U.S. service personnel in the country on exchange.

Air combat units also use the expansive live bombing ranges in Australia’s sparsely populated north in training rotations of a few months, and occasionally naval units train off the coast. But training exercises involving ground forces are unusual.

Obama had scrapped two earlier visits, once to stay in Washington to work for passage of his health care bill, and again after the oil spill in the Gulf of Mexico.

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Associated Press writers Erica Werner and Rod McGuirk in Canberra contributed to this report.