German carmaker Opel, a loss-making unit of US giant General Motors, is in talks with unions over a reduction of working hours at its main plant in Ruesselsheim, near Frankfurt, unions said Thursday. \"Given the deterioration of the market in Europe, the management of Adam Opel AG is currently negotiating with the workers\' council and the IG Metall labour union with regard to short-time work and a reduction in working hours in Ruesselsheim,\" the union said in a statement. \"The outcome of those talks is expected shortly.\" A spokesman for Opel insisted that \"nothing has been decided yet.\" Ruesselsheim, which also acts as Opel\'s headquarters, is the carmaker\'s main and biggest production site, manufacturing the Insignia and Astra models. Some 13,800 people are employed at the site, including 3,500 in production and more than 10,000 in administration, design and development. Troubled Opel is part of GM\'s European operations which have run up billions of dollars in losses over the past 10 years. GM had planned to sell Opel at one stage but pulled back when it could not find a suitable buyer.