David Sanger: A leader now at the mercy of behemoth he helped create

With president Hu Jintao at the helm, China has become an industrial colossus, a growing military force, and, it sometimes appears to a confused West, a model of authoritarian decisiveness, navigating out of the global financial crisis and sealing its position as the world's fastest rising power.

But Obama administration officials are grappling with what they describe as a more complex reality. China is far wealthier and more influential, but Mr Hu also may be the weakest leader of the Communist era.

His strange encounter with US defence secretary Robert Gates in Beijing last week - in which Mr Hu was apparently unaware that his own air force had just test-flown China's first stealth fighter - was only the latest case suggesting that he has been boxed in or circumvented by rival power centres.

US officials have spent years urging Mr Hu to revalue China's currency, rein in North Korea, ease up on dissidents and crack down on the copying of technology. But those problems have festered, and after first wondering if the Chinese leader was simply deflecting them or deceiving them, Barack Obama's top advisers have concluded that Mr Hu is often at the mercy of a diffuse ruling party, in which generals, ministers and big corporate interests have more clout than they did in the days of Mao or Deng Xiaoping, who commanded unquestioned authority.

China's military has more recently sometimes pursued an independent approach to foreign policy. So have many of China's biggest state-owned companies.

"There is a remarkable amount of chaos in the system, more than you ever saw dealing with the Chinese 20 years ago," said Brent Scowcroft, the former US national security adviser.

Not surprisingly, some of the biggest differences focus on how to deal with the United States and its power in the Pacific.

Mr Hu has repeatedly asserted China's disinclination to challenge US power; his foreign policy co-ordinator, state councillor Dai Bingguo, recently wrote an article reaffirming Deng's warning, made when China's modernisation was beginning, that it should bide its time before seeking a global role.

Last Friday, the article was cited by Mr Obama's national security adviser, Thomas Donilon, who characterised it as "a definitive statement at this point of the leadership's approach to foreign policy generally and the US specifically". However, he then acknowledged debates "particularly in the blogosphere and in newspapers in China" that urge a far faster, more assertive rise, and that trumpet American decline.

Adding to the uncertainty about Mr Hu's power is an expected leadership change in 2012.It is at once a choreographed transition to a new generation of leaders and a minefield for all contenders, none of whom wish to be viewed as risk-takers, or as subservient to the US - or any other foreign power.