By Agence France-Presse Opel, the troubled German car maker belonging to U.S. auto giant General Motors, is expected to turn a sharply higher operating loss this year than last year, informed sources said on Wednesday. Opel, which booked operating loss of 384 million euros ($522 million) in 2003, is expected to turn a figure of "at least" 600 million euros this year, the sources said. Nevertheless, Opel was expected to return to profit at operating level in 2005, the sources added.