US officials and experts say conflict between the Asian powers remains unlikely, with both sides keen to preserve economic ties, and neither likely to emerge as a clear winner.

Nevertheless, as naval vessels spar in disputed waters and fighter jets patrol disputed skies, the risk of accidents or miscalculations has risen. Maintaining peace in Asia's seas has become a major US concern in the year ahead, officials say.

Obama had hoped his foreign policy "pivot" towards Asia would shift America's attention away from trouble spots like Afghanistan and Iraq and toward a region brimming with economic opportunities. He has aimed to strengthen longstanding alliances in Asia and bring new resolve to managing a relationship with China.

But experts say the US effort to deepen relations with China and its traditional Asian allies could be an impossible balancing act.

"In a perfect world you could do both simultaneously without conflict, but in practice, whatever you do with one side, the other side sees it as being done against them," says Ely Ratner, senior fellow at the Centre for a New American Security in Washington.

Daniel Russel, assistant US secretary of state for East Asian and Pacific affairs, says the security umbrella provided by Washington has preserved regional peace for decades. The rebalance merely reinforces that commitment to Asia in a time of rising Chinese influence and assertiveness, he argues.

But some experts say that the new emphasis on strengthening security links with Japan, South Korea, Vietnam, Australia and the Philippines could actually be raising regional tensions.

"It is only encouraging those in China who have been saying for some time that Americans have reverted to cold war thinking, and this is part of a containment strategy," says Mel Gurtov, a professor of political science at Portland State University, and editor of the journal.

America's alliance with Japan means the US is far from a neutral party in the China-Japan spat, "and the most important relationship we have to cultivate, with China, is bound to suffer".

In a sign of the increasing strain on US-China relations, American lawmakers warned last week at a House subcommittee hearing that the United States must not tolerate China's use of military coercion in pursuit of its territorial claims. Beijing's nationalist newspaper responded by arguing that US meddling risked "triggering an all-out confrontation with China" - although the paper simultaneously advocated restraint and co-operation.

Tensions escalated in late November after China imposed an air defence identification zone over vast swathes of the East China Sea, including over islands administered by the Japanese. It demanded that all noncommercial aircraft entering the zone identify themselves or face "defensive emergency measures".

Calling China's bluff, the US flew two B-52 bombers through the zone within days.

Then in December, Abe visited the Yasukuni Shrine in Tokyo, where 14 war criminals are honoured among 2.5 million war dead. That stoked anger in China and South Korea, where memories of Japanese wartime atrocities remain fresh, and prompted Beijing to declare that Abe had "shut the door to dialogue".

US efforts to calm tensions have so far had little apparent effect. Indeed, it is not clear if either side is paying Washington much attention. US officials say they learned less than an hour in advance about China's air defence zone - which was announced just before Vice-President Joe Biden's visit to the region - and got little notice about Abe's visit to the shrine.

Russel says the roll-out of China's air defence zone has increased the risk of "miscalculation and an accident" that could lead to conflict.

"This was not simply a failure to communicate," he says. "It was an action that bypassed a consultative, collaborative process, and is a type of behaviour that is inconsistent with the stature and status that China clearly seeks in the region."

Abes visit to the Yasukuni Shrine, he says, was a concern of a much lower order of magnitude, but was nevertheless "very disappointing."

Russel says Obama's efforts to build a relationship with President Xi Jinping improved channels of communication and gave Washington the chance "to speak directly and very candidly to China about our concerns".

Nevertheless, Beijing is not backing down from its territorial claims. It has announced an effort to exert tighter control over fishing in the South China Sea waters, which are contested by countries such as Vietnam and the Philippines. The US State Department called that move "provocative and potentially dangerous".

For Washington, the priority is crisis management - getting both sides to agree to rules of engagement in contested waters and skies, as well as encouraging them to set up hotlines.

"In the short term there is a crying need for a practical mechanism to prevent crises or manage them should they occur," Russel says. "The critical thing in the short term is that no incident be allowed to trigger an escalatory cycle, and the environment and structures be put in place that minimise the risk of an incident taking place at all."

The problem is that leaders on both sides are more concerned with appeasing domestic nationalists and not losing face than listening to their foreign friends.

Back-channel diplomatic links have dried up, while even business and cultural visits and exchanges between Japan and China have been cancelled in recent weeks.

"Without a summit to show some thaw in political relations, there is very little diplomats or line agencies can do to walk back tensions, or talk about any of the crisis management that is needed," says Yanmei Xie, with the International Crisis Group.

Abe's Yasukuni Shrine visit also widened the divide between America allies Japan and South Korea. Beijing is already exploiting that divide, trying to strengthen its economic and diplomatic ties with Seoul and isolate Tokyo.

Christopher Johnson, senior adviser at Washington's Centre for Strategic and International Studies, says the Obama administration's toolkit for resolving the problem is limited. "We have rhetorical pressure, which we are using, and we have the Seventh Fleet, which nobody wants to use, and in between our options are more constrained," he says.

In April, Obama is scheduled to visit Asia but will bypass Beijing - ostensibly because he will be travelling there later in the year for an Asian summit.

"The Chinese are likely to read more menacing implications into the decision," says Johnson.