He was wrongly reported dead last year, and his political influence was said to have faded as a younger generation assumed control of China, but former President Jiang Zemin has made a surprise comeback.

As the Communist Party readies to unveil its new leadership line-up on Thursday, Jiang's fingerprints -- or at least those of the faction for which he serves as an eminence grise -- seem increasingly clear on the transition.

Jiang entered Beijing's cavernous Great Hall of the People for the opening of the party's congress last week directly behind outgoing general secretary Hu Jintao and sat next to him, dozing intermittently.

Analysts say the 86-year-old Jiang's prominence at the congress reflects his continued impact on behind-the-scenes negotiations to pick China's next crop of top leaders.

Jiang loyalists, they add, are likely to make up the core of China's most senior decision-making body, the Politburo Standing Committee, to be headed by current Vice President Xi Jinping who is widely viewed as a consensus figure.

Observers associate Jiang, who guided China into the World Trade Organization and allowed entrepreneurs into the party for the first time, with more business-friendly, free-market economic policies.

Hu's camp is said to favour a greater role for the state in the economy, and emphasises fairer distribution as well as economic growth.

But the differences are apparently more personal than political.

"Jiang plays the role of kingmaker," said Willy Lam, a political analyst at the University of Hong Kong who wrote a biography of Jiang. "He has been very effective in this factional struggle."

The role of geriatric party figures in the secret discussions which determine China's leadership is played down by the Communist party, which says that its leaders are picked during the congress through elections by delegates.

Zhang Chunxian, the party chief of the restive western province of Xinjiang, who is reportedly an ally of Jiang, refused to comment when asked about the ex-president's continued influence by an AFP reporter.

"That sounds like gossip... I don't know where you get your information from," he said, laughing dismissively.

Jiang, who held the Communist party's top post from 1989-2002, was pronounced dead by a Hong Kong TV station in 2011 after a period of illness, prompting furious speculation.

But a healthy-looking Jiang has made several high-profile appearances this year, in what analysts see as an attempt to display his political credentials ahead of the congress -- where he sported a shock of nut-brown dyed hair.

His leverage on party negotiations was boosted by a recent scandal involving Hu's close political ally Ling Jihua, who according to reports attempted to cover up a Ferrari crash that killed his son, who had two young women in the vehicle.

But Jiang's motivation for reasserting his influence is likely to be more about protecting family interests than promoting a political agenda, analysts said.

"In the run up to the congress Jiang wants more of his proteges to be promoted to ensure his legacy and protect his two children," Lam said.

Jiang's son Jiang Mianheng, the high-profile head of an investment firm, has brokered deals with foreign firms including Microsoft and Nokia. His younger son is the director of a research centre.

"Because his two sons are doing a lot of business, they might be exposed to allegations of corruption," Lam said. "Jiang wants to make sure he can protect them from that."

Jiang has jockeyed into place several allies on the Politburo Standing Committee, leaving outgoing Hu with fewer loyalist on the body.

"In terms of people who will unquestioningly do Hu's bidding there's only one: Li Keqiang," Lam said, referring to the man expected to become China's new premier.

But Hu has ensured that his own loosely connected group of allies will have long term influence, by promoting his associates into top posts in the military and as regional party chiefs.

"I suspect Jiang's influence might not last beyond the Congress. He is trying to pull some strings but is not a powerful figure," said Steve Tsang, professor of contemporary Chinese studies at Britain's University of Nottingham.

Jiang's power is also threatened by continuing doubts about his health, and a likely push by Xi to assert himself once he assumes the top party post, observers say.