Berlin - Bids from companies vying for control of German carmaker Opel have so far proved unsatisfactory, German Economics Minister Karl Theodor zu Guttenberg was quoted as saying on Sunday.

"We now have three offers to take over Opel. That does not mean that one of them will automatically and urgently take effect," he told the newspaper Bild am Sonntag.

"Firstly, we need a high degree of certainty that the considerable sum of taxpayers' money we will have to put up is not lost. None of the three plans sufficiently meets these requirements at present," the minister said.

Canadian-Austrian car parts and assembly group Magna, Fiat of Italy and the European holding company of US-based private-equity group Ripplewood have submitted bids for the General Motors subsidiary.

China's Beijing Automotive Industry Holding Co. (BAIC) has also expressed interest in securing a stake, but has not formally made an offer.

Magna, which has pledged to keep open all Opel plants in Germany but slash 10 per cent of the 25,000 workforce, has emerged as the front-runner to take over the carmaker.

But leaders of the four German states where Opel has factories were divided on the offer. North Rhine-Westphalia premier Juergen Ruettgers said the plan was unacceptable to him because the bulk of the German job losses would be in his state.

German officials declined to comment on reports that Magna wanted Berlin to take over 3 billion euros (4.2 billion dollars) in Opel pension commitments.

Fiat chairman Sergio Marchionne told Bild am Sonntag that a maximum of 2,000 jobs would be lost in Germany under a revised bid submitted by the Italian carmaker.

Canada-based Magna, which has extensive operations in Austria, filed its proposal in conjunction with Russia automotive group GAZ and Russia's Sberbank.

The final decision on the future of GM's European operation will be reached by GM and the US government, but Germany has a stake in the decision as any outcome is likely to rely on German state guarantees.

Magna said it wants the German government to make available 4-5 billion euros (5.6-7 billion dollars) in guarantees to support the new operation.

Zu Guttenberg said Germany's preference would be made known this week, but did not rule out Opel going into insolvency if the final bids fail to meet Berlin's requirements.

Meanwhile, GM must present the US government with a viable strategy for survival by May 29 or risk possible bankruptcy.(dpa)