In this March 6, 2017 photo, Sun Zhengcai, then party secretary of Chongqing, attends a meeting on the sidelines of the National People's Congress at the Great Hall of the People in Beijing, China. Former Chinese political high-flyer Sun is standing trial Thursday, April 12, 2018, for bribery in eastern China, making him one of the highest-level officials to be prosecuted in President Xi Jinping's sweeping anti-corruption campaign. (AP Photo/Ng Han Guan)

BEIJING - A former Chinese political high-flyer who has been accused of plotting against the ruling Communist Party pleaded guilty to bribery on Thursday, setting the stage for one of the highest-level convictions in President Xi Jinping's campaign against corruption and political disloyalty.

Sun Zhengcai, former party leader of the western megacity of Chongqing, pleaded guilty to the charges in court and expressed repentance, according to the No. 1 Intermediate People's Court in the eastern city of Tianjin.

Sun and his alleged associates were accused of accepting money and assets worth 170 million yuan ($27 million) in return for providing help to unspecified organizations and individuals with engineering contracts, business operations and other matters, the court said.

He had been a member of the party's elite 25-member Politburo and had been seen as a candidate for promotion to the Politburo's Standing Committee, the select group of leaders who constitute the apex of political power in China.

Chinese leaders and party-run media have made it clear that though Sun was accused of corruption his alleged offences were largely political in nature.

The chairman of China's securities regulator said at a major party meeting last year that Sun and other senior figures prosecuted in the crackdown were "conspiring openly to usurp party leadership."

Sun was expelled from the party and dismissed from public office in September because he was suspected of "serious discipline violations," a phrase that usually refers to bribery but increasingly also includes political disloyalty.

He was removed suddenly from his Chongqing post and replaced by Xi protege Chen Min'er, who was subsequently promoted to the Politburo.

Sun had been identified most closely with the China Youth League faction associated with Xi's predecessor, Hu Jintao, which Xi had effectively sidelined in the succession process.

The court said on its official page on the social media site Weibo.com that Sun said he had only himself to blame for his crimes. Sun could not be reached for comment.

News from © The Associated Press, 2018