The new president of China's 1.35 billion people is a relaxed, affable contrast to his stiff predecessors -- but whether there will be an accompanying change of substance remains to be seen.

Xi Jinping's first months in power as head of the ruling Communist Party have shown a "new style, but short on delivery so far", said Jean-Pierre Cabestan of Baptist University of Hong Kong, describing him as "old wine in a new bottle".

The 59-year-old is the first Chinese leader to have been born after the Communists took power in 1949, and is one of the party's "princelings" -- the privileged offspring of those who played key roles in the revolution.

Xi was named head of state by the rubber-stamp national parliament on Thursday. But he became China's de-facto supremo in November, when he was elevated to lead the all-powerful Communist Party.

Since then, a barrage of official propaganda has promised reforms on issues ranging from pollution to corruption, while Xi and others have made high-profile tours of poverty-stricken villages.

Warning that corruption could "kill the party", Xi threatened in January to target not only lowly "flies" but also top-ranking "tigers".

An investigation by US news agency Bloomberg last year, however, found that Xi's relatives had amassed hundreds of millions of dollars in assets, hinting at the challenge of implementing reforms that might threaten the business interests of powerful families.

To underscore a commitment to economic reforms, Xi chose the southern city of Shenzhen, where China launched its modernisation drive three decades ago, for his first official visit as party leader.

But any desire for fundamental reforms is likely to be tempered by the overriding fear that drastic change could weaken party control.

Xi reportedly warned officials during his southern trip against letting the party unravel as the Soviet Union did, saying that Gorbachev-style reforms could undermine Communist control.

He rose to the top of the secretive party by serving as a compromise pick able to navigate between competing factions, including those of outgoing leader Hu Jintao and the influential former president Jiang Zemin.

Xi has an impeccable political pedigree as the son of a revolutionary hero, and has a pop star wife, Peng Liyuan, who holds the rank of army general and starred in state broadcaster CCTV New Year's gala for years.

But his father Xi Zhongxun, a respected Communist elder, was purged during the 1966-76 Cultural Revolution, and Xi himself was sent to the Chinese countryside to live and work alongside peasants, as were many educated youths.

Xi joined the Communist Party while labouring in the poor northern province of Shaanxi and in 1975 moved to Beijing to study at the prestigious Tsinghua University, earning a degree in chemical engineering.

He went on to oversee some of China's most economically dynamic areas, including Fujian and Zhejiang provinces and Shanghai, earning himself a reputation as a proponent of economic reforms and an effective manager.

He created a stir during a 2009 speech in Mexico by scoffing at "foreigners with full bellies and nothing to do but criticise our affairs" -- many Chinese harbour resentment against the West -- but he has unusually longstanding US links for a Chinese leader.

As part of a research trip in 1985 he spent time in Iowa, deep in the farming heartland of the Midwest, and paid his host family a return visit last year, while his daughter Xi Mingze studied at Harvard under a pseudonym.

A diplomatic cable released on WikiLeaks recounted a 2007 conversation between Clark Randt, the then US ambassador to China, and Xi that revealed the future president as a big fan of US films on World War II.

He told Randt that he "tremendously enjoyed" the 1998 Steven Spielberg war epic "Saving Private Ryan", the cable said, adding that Xi noted: "Americans have a clear outlook on values and clearly demarcate between good and evil. In American movies, good usually prevails."

The cables described Xi as pragmatic yet ambitious, willing to tilt with the political winds to get ahead.

They said he was uncorrupted by money yet with a sense of political entitlement, feeling that fellow "princelings" like him "deserve to rule China".

As of Thursday, he fulfils his destiny. But like all incoming Chinese leaders he will need to consolidate power, and whatever his personal beliefs, few expect him to stray far from the Communist template of gradually opening the economy while maintaining tight political control.

Cabestan added: "Frankly I don't see him as a reformer."