German economy minister Karl-Theodor zu Guttenberg said on a Friday TV broadcast the government expected the General Motors board to make a "fundamental decision" on the future of Opel next week.

Guttenberg said there were offers for Opel which were ready to be signed and that it was time for its US parent to "give in".

"We're still negotiating towards an investor solution - that is an industry-based plan which will be valid in the longer term," he said, suggesting Berlin did not expect Opel to stay with GM, a possibility that has recently gained currency.

The German government has been pushing GM to accept a bid for Opel by Canadian auto parts group Magna, though Belgian-based investor RHJ is also in the running, Reuters noted.

GM Europe head Carl-Peter Forster told Die Welt he believed Magna was most likely to win a bidding battle for Opel, but that the carmaker could also thrive under the ownership of its US parent.

"The greatest probability would be, for me, Magna, since all prerequisites are fulfilled, the contracts have been negotiated to their conclusion, and the financing is there," he was quoted as saying.

But company sources told Reuters Forster - whom Magna has requested to stay on to run Opel should it win the deal - was not speaking for management which favoured either a rival bid from RHJ or, increasingly, no sale at all.

Chancellor Angela Merkel told the Westdeutsche Allgemeine Zeitung daily she still expected Opel to be hived off from GM.

"We have no indication that GM is moving away from an investor-based solution," Merkel was quoted as saying.

Opel senior labour leader, Klaus Franz, on Thursday threatened General Motors that his workforce would not help to reduce around US$1.2bn in costs if GM US remained in charge at the European unit.