Opel, the troubled German car maker belonging to US auto giant General Motors, is expected to post a sharply higher operating loss this year than last year, sources said on Wednesday. Opel, which booked operating loss of €384 million ($522 million) in 2003, is expected to register a figure of "at least" €600 million this year, sources said. Nevertheless, Opel was expected to return to profit at operating level in 2005, they added.