General Motors' Opel subsidiary says it's in talks with unions to reduce work hours at two major plants in Germany as it struggles with a drop in demand for its vehicles.

The dapd news agency reported Thursday that Opel said it is in talks to shorten hours at its main plant in Ruesselsheim and at a smaller plant in Kaiserslautern. An agreement is expected soon.

The company wouldn't say how many workers could be affected, but Ruesselsheim employs some 13,000 people and Kaiserslautern 2,500.

GM has been shaking up Opel in recent weeks, replacing many top managers including its CEO, CFO and head of research and development.

GM has made clear it is determined to return to profitability its money-losing European business, which includes Britain's Vauxhall, despite tough competition among mass-market carmakers.