As the United States moves to bolster its military position in Asia, it faces severe budget cuts from Congress, an increasingly powerful rival in China and a hornet's nest of regional political sensitivities.

The shift in U.S. policy puts Asia and the Pacific front-and-center of its strategic priorities and is driven by concerns that China has raced ahead in the world's most economically dynamic region while the U.S. was tied up fighting its wars in Iraq and Afghanistan. But in a region rife with disputes and increasingly beholden to China's economic engine, the Pentagon is being careful its "pivot to the Pacific" doesn't create too many waves.

Defense Secretary Leon Panetta, who is spearheading the U.S. effort to sell the new strategy in Asia, told regional defense leaders at a major security conference in Singapore that it is only natural for the Asia-Pacific to be in the spotlight because it is home to some of the world's biggest populations and militaries.

Before moving on to Vietnam and India, Panetta said Washington will "of necessity" rebalance toward the Asia-Pacific region and vowed 60 percent of the Navy's fleet will be deployed to the Pacific by 2020. He said the U.S. presence will be more agile, flexible and high-tech. Troops may increase overall, but no major influx is expected.

Long-term allies such as Japan, Australia and South Korea strongly support a robust U.S. presence and see the shift as a welcome development.

"The U.S. has made the Asia-Pacific its top priority to reflect the fact that the world economic center of gravity now resides in this region," said Carlyle Thayer, a professor at the University of New South Wales, in Australia.

But others worry the U.S. could try to isolate China, at the rest of Asia's expense.

"With their enormous economic potentials, it is natural that many countries want to build good relations with both China and the United States," Indonesian President Susilo Bambang Yudhoyono said at the three-day Singapore meeting, which ended Sunday. "Asia is certainly big enough for all powers — established and emerging."

U.S. officials stress they are not seeking new permanent facilities on foreign shores and instead are looking at a slew of less-threatening and less-expensive deals to rotate troops into existing bases throughout the region, step up joint military maneuvers and push for access to key ports.

"This is not a Cold War situation in which the United States charges in," Panetta said. He assured his audience that U.S. budget problems and cutbacks of nearly $500 billion over the next decade would not get in the way of changes, and he said the Defense Department has money in its five-year budget plan to meet its goals.

The United States has for decades maintained tens of thousands of troops in South Korea and Japan. But while Washington was waging its wars elsewhere and staying relatively static in Asia, China was vastly improving its military.

Beijing has used a 500 percent increase in defense outlays over the past 13 years to develop everything from better submarines and missiles to state-of-the-art fighters, aircraft carriers and electronic warfare systems. That has helped spawn an arms race across Asia — which now has the world's top five arms importers and will this year surpass Europe in total arms expenditures.

Concerns over China in the past were focused mostly on its claims to Taiwan, which it considers a renegade province. But that has broadened out to Beijing's increasingly aggressively claims to the South China Sea, where it has territorial disputes with a half dozen countries.

Those rival claims came to a head in April, when the Philippine navy accused Chinese boats of fishing illegally around Scarborough Shoal, which Manila claims as part of its exclusive economic zone, but which Beijing insists has been Chinese for centuries. The standoff has yet to be resolved, though no shots have been fired.

China says its actions are justified.

"China will be especially cautious about using military force to solve the disputes," an op-ed in the China Daily newspaper said last week. "China sticks to a defensive national defense policy, but it will firmly defend its sovereignty and territory to the best of its ability, just as any other country would."

Even so, Beijing's perceived heavy-handedness in such confrontations appears to be strengthening Washington's hand:

— Singapore has agreed to allow the U.S. to deploy four new Littoral Combat Ships designed to fight close to shorelines to its main naval port starting next year. But to avoid the appearance of opening up too much, it has demanded the ships' crews live on board while in port and their families stay elsewhere.

— Indonesia, which had only limited military relations with Washington in the 1990s because of U.S. human rights concerns, is now looking to buy a broad range of American hardware and is joining in joint maneuvers.

— The Philippines, which kicked U.S. forces bases off their soil in 1992, is actively courting increased U.S. military support, including allowing more troops in on a rotational basis.

Washington is already testing out that approach in Australia, which has agreed to allow up to 2,500 Marines to deploy to the northern city of Darwin. The Marines will use Australian facilities, not a new U.S. base, and the plan has met with little opposition. The first detachment of Marines arrived in April.

Most of the troops going to Darwin were freed up by another deal aimed at placating a key ally — an agreement with Tokyo this year to move about 9,000 Marines off of the island of Okinawa.