German engineering trade union IG Metall has again demanded Volkswagen's management present a detailed restructuring plan for the carmaker's troubled VW brand ahead of negotiations to be held on Monday.

"Volkswagen has to lay its cards on the table. We want to know how Volkswagen aims to restructure its core Volkswagen brand and what concrete demands will be placed on IG Metall," regional union boss Hartmut Meine said in a statement cited by the Reuters news agency on Friday.

"Only then will we decide whether to enter into wage negotiations with Volkswagen," he reportedly continued. Preliminary talks are scheduled to be held at 1230 GMT on Monday in the northern German city of Hanover, the report said.

Citing the Financial Times Germany, Reuters reported that both sides have already agreed to the valuation method to be employed in the case of VW's uncompetitive components operations, which could serve as a basis for these to be sold or closed down.

VW AG has said that up to 20,000 jobs at the VW brand are at risk as a result of its efforts to boost productivity and efficiency in Germany, the report added.

The carmaker's in-house wage agreement with IG Metall reached in November 2004, however, does not permit forced layoffs for any of the 100,000 workers in the company's six western German plants until 2012, Reuters said.