HSBC Holdings PLC Chairman Stephen Green is to step down to become Britain's trade minister, and a competition to succeed him formally began.

The London banking company plans to tap Green's successor by yearend, it said Tuesday. Green is to start in government in January.

CEO Michael Geoghegan and former Goldman Sachs partner John Thornton are "viable" candidates to succeed Green, said Colin Mclean, who manages $999 million, including HSBC shares, at SVM Asset Management in Edinburgh.

Geoghegan, who succeeded Green as CEO in 2006, issued a statement lauding his predecessor's contribution. "For HSBC it is business as usual; I continue to run the company," he said. Thornton joined HSBC as nonexecutive chairman of its North American unit in late 2008.

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