BEIJING (REUTERS) - China on Saturday (July 15) named rising political star Chen Min'er as Communist Party boss in south-western Chongqing municipality, cementing his reputation as a favourite of President Xi Jinping ahead of a leadership reshuffle at a key party congress in the autumn.

The elevation of Chen, a trusted confidant of Xi, is a sign the President is flexing his political muscles as he manoeuvres to line up a new Politburo Standing Committee, the apex of political power in China.

Chen previously worked under Xi in Zhejiang province, where Xi was then provincial party leader, and has since ridden the coat-tails of his former boss, climbing rapidly through the party ranks.

Foreign diplomats who have met Chen say he talks openly about his closeness to Xi. Chen, who moves to Chongqing from the poor south-western province of Guizhou, takes over from Sun Zhengcai, China's official news agency Xinhua said in a brief report, without saying where Sun would go next.

Chen, who moves to Chongqing from the poor south-western province of Guizhou, takes over from Sun Zhengcai, the official news agency Xinhua said, without saying where Sun would go next or including wording to suggest he would get another position.

Chongqing television's main evening news showed Chen giving a speech to senior city officials, telling them he would not let down the party's trust in giving him such an important job. His predecessor Sun did not appear to be present in the meeting.

Chongqing is perhaps best known for its association with its disgraced former party boss Bo Xilai, once himself a contender for top leadership before being jailed for life in 2013 in a dramatic corruption scandal.

Chen said officials must "resolutely eliminate the malign influence" of the Bo case, Chongqing television reported.

Chen was made Guizhou deputy party secretary in 2012, but was promoted to governor less than a year later and within roughly a month of Xi becoming President, before moving up again to his current role as Guizhou party boss in 2015.

Sources with ties to the leadership had said Chen could jump straight into the Standing Committee with Xi's support potentially easing out contenders from rival factions, though Chen is still considered a dark horse candidate.

The switch from Guizhou to the more high-profile Chongqing role signals that Chen is virtually assured of a Politburo spot.

But the change so close to the 19th Party Congress may mean he has to wait longer for further promotion, as it would be unusual to move the holder of such an important post within months.

Sun had been seen as another potential candidate for elevation, but his star has waned. Sources with ties to the leadership and foreign diplomats say Sun has been out of favour after the party's anti-corruption watchdog this year criticised Chongqing authorities for not doing enough to root out Bo's influence.

For decades, Guizhou was one of China's most backward provinces, but in recent years the central government has poured in billions of yuan, with a focus on poverty alleviation and big data.

Xinhua said Guizhou governor Sun Zhigang, who is not related to Sun Zhengcai, had taken over as the province's party chief.