Chinese media reported today that Jiang, 86, hosted a "family-like" meeting and banquet for the visiting former US secretary of state in Shanghai on July 3, during which Jiang extolled the virtues of the new head of the Communist Party, Xi Jinping.
"Xi Jinping is an extremely capable and wise state leader," Jiang was described as saying in an official announcement about the meeting issued by the Foreign Ministry on Monday.
"Although China currently has to overcome many difficulties, I am confident with the new leadership of China," Jiang said.
Jiang's appearance in the Chinese media is rare since he made a symbolic move in January to step out of the public view, though it remained unclear whether he would relinquish his behind-the-scenes influence in the leadership.
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When Xi's predecessor Hu Jintao was appointed party leader a decade ago, his efforts to consolidate his power were blocked by Jiang's retention of powerful chairmanship of the party commission that oversees the military. Jiang's support for Xi could help strengthen the new leader's authority.
Jiang is foremost among the party's retired elders, who enjoy tremendous clout even though they typically have no official posts.
He oversaw a four-fold expansion of the economy, the reversion of Hong Kong from British to Chinese rule, and the country's entry into the World Trade Organisation.
Jiang stepped down as party leader in 2002, although he led the commission that controls the armed forces for another two years.
His praise of Xi who took over as party boss last November and as president in March is being interpreted as a bid to show solidarity in the highest echelons of the Communist Party.
Such unity helps bolster Xi's new administration as it tries to undertake promised economic reforms and show that it's cleaning up widespread corruption in party ranks.
The government has also had to tackle violent unrest in the ethnic minority region of Xinjiang and massive protests over environmental pollution.