BEIJING - China's outgoing President Hu Jintao promised political reform on Thursday, saying the nation faced risk and opportunity in equal measure as he formally opened a congress of the ruling Communist Party that will usher in a once-in-a-decade leadership change.

More than 2,000 hand-picked delegates gathered at Beijing's cavernous Great Hall of the People for the start of the week-long session, held against a backdrop of growing social unrest, public anger at corruption and a yawning gap between rich and poor.

"Reform of the political structure is an important part of China's overall reform," Hu said in an opening speech. "We must continue to make both active and prudent efforts to carry out the reform of the political structure and make people's democracy more extensive, fuller in scope and sounder in practice."

But nobody expects a move towards full democracy and party spokesman Cai Mingzhao made clear on Wednesday that one-party rule was inviolate.

During the congress, Hu will give up his role as party chief to anointed successor Vice President Xi Jinping. Xi then takes over state duties at the annual meeting of parliament in March.

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