BERLIN: Labor representatives at General Motors' loss-making European unit Opel told the car maker's management they will not discuss restructuring measures on a plant-by-plant basis.

"We will not negotiate with you on a local level," European labor representatives said in an open letter to Opel Chief Executive Officer Karl-Friedrich Stracke published on Monday.

Management will on Wednesday present to Opel's supervisory board a mid-term business plan that currently foresees the closure of two plants, according to labour sources.