* Rapid succession of visits to and from Asia-Pacific
* Asians torn between US security assurances, China's market
* Some say America's relative decline limits appeal
WASHINGTON - An intense fortnight of top-level U.S. engagement with Asian countries from powerful India to tiny Singapore has highlighted President Barack Obama's seriousness about reasserting American power across the Pacific - but also the obstacles he faces.
Even as a conflict elsewhere, in Syria, worsened dramatically this month, the Obama administration's top officials spent much of their face-time with Asian colleagues.
Defense Secretary Leon Panetta toured Singapore, Vietnam and India; Obama hosted Philippine President Benigno Aquino at the White House; and Secretary of State Hillary Clinton welcomed counterparts from Cambodia, Thailand, India and South Korea.
Virtually every country on the list is a potential friction point between the United States and a rising China, and many share Washington's concern about Beijing's increasing economic and military influence.
"All of this happening at the same time does a very good job of conveying the message that we are paying attention to the region, that it's of great importance to us and that we intend to focus on it even more," said Michael Mazza, a security expert at the American Enterprise Institute in Washington.
But meetings and messaging may be the easy part, Mazza and other analysts say.
China's rapid military build-up and its tough stance on territorial disputes with weaker Southeast Asian neighbors has inadvertently given a boost to Obama's enhanced Asia strategy, variously called a pivot, a refocus or a rebalancing.
But ahead still lies the harder work of matching the expectations of Washington's partners - including mustering the political will to overcome U.S. fiscal deficits and dispelling a growing sense that the United States is declining while China rises.
U.S. policy also has to factor in historical ambivalence about the United States in India and several other regional democracies, as well as political disarray in long-time ally Japan.
Countries with troubling human rights records like Vietnam and Cambodia have limited appeal in the U.S. Congress, while leaders of these states see political risks in getting too close to Washington.
And the U.S. strategy, while drawing some verbal fire from China, has yet to be tested in a serious way. That might happen if, for example, the Philippines' ongoing showdown with Beijing over contested shoals in the South China Sea were to deteriorate into a military conflict that invoked U.S. Mutual Defense Treaty obligations to Manila.
POLITE FICTION, ECONOMIC REPRISALS
The official U.S. line that its more energetic Asia-Pacific diplomacy is "not directed at any one country" is scarcely taken at face value - not least in that unnamed one country.
"In Australia's case, it is a matter of doing what the United States wants while reassuring China it is not a containment policy," said Australian National University analyst Michael McKinley. "The Chinese don't believe it."
But the polite fiction employed by Washington serves Asia-Pacific countries who seek security assurances from the far-away United States without sacrificing important trade with nearby China and its fast-growing economy.
"Treading too forcefully on China's interests can and has resulted in economic reprisals against Southeast Asian countries," said Scott Harrison of Pacific Strategies and Assessments, a consultancy in Manila.
Beijing responded last month to its South China Sea dispute with Manila by tightening quality controls on Philippine fruit and cutting the number of visits by Chinese citizens to the Philippines.
For now, many nations in Asia have welcomed the U.S. pivot despite the danger of antagonizing Beijing, said Ross Babbage, a defense analyst and founder of the Kokoda Foundation, an independent security policy unit in Canberra, Australia.
"What you are seeing is key players in the region playing their cards differently," he said.
Australia and other traditional U.S. allies have publicly backed Washington's new strategy, while others, such as Vietnam, have quietly but enthusiastically sought closer ties to counter China's "turbo-charged" military expansion, Babbage said.
Threatened by China's growing assertiveness, Manila sees Washington's new Asia policy as "essential to ameliorate its growing security dilemma," said Rommel Banlaoi, head of the Center for Intelligence and National Security Studies of the Philippine Institute for Peace, Violence and Terrorism Research.
DECLINE TALK, BUDGET CUTS
When Australia's Defense Minister Stephen Smith visited China this month for inaugural bilateral defense talks, he was forthright about Canberra's decision to host 2,500 U.S. Marines for training missions in Darwin.
"There's no inconsistency between Australia continuing an alliance with the United States and developing a comprehensive relationship with China," he told skeptical Chinese academics.
Some regional security experts, however, say the renewed U.S. emphasis on Asia has emboldened China's opponents in the South China Sea dispute, an outcome Washington might not have intended.
"The U.S. becoming involved has fired up the Philippines and Vietnam to contest things more strongly," said Sam Bateman, a retired senior Australian naval officer and maritime security researcher at Singapore's Nanyang Technological University.
Washington's intentions aside, U.S. political gridlock, fiscal deficits and slow economic growth compared to China raise doubts in the region about American staying power.
"The United States needs lots of partners because its own capabilities are in a sense in relative decline," said McKinley from the Australian National University. (Additional reporting by David Alexander and Jack Kim in Seoul, Manuel Mogato in Manila, David Lague in Hong Kong and James Grubel in Sydney; Editing by Warren Strobel and David Brunnstrom)