The German government has said it would select its preferred bidder for Opel and Vauxhall's operations as early as tomorrow. Although the sale is ultimately the decision of parent General Motors, the government has a say as it would likely provide billions of euros in financing guarantees.

According to media reports in Germany, Magna International, North America's largest components supplier, is favourite although Fiat has improved its offer. Belgian holding group RHJ International is also in the running.

Spokesman Ulrich Wilhelm said the government plans to "clarify the Opel question by the middle of this week. The government's aim remains to keep all four Opel plants in Germany open and to prevent an insolvency."

Wilhelm added that, while talks were continuing with all three bidders, discussions had been most intense with Fiat and Magna because their offers were the most complex. At the weekend, economy minister Karl Theodor zu Guttenberg said the bids were inadequate and suggested an orderly insolvency might be the best way to rescue at least a part of Opel, which employs around 25,000 in Germany.

Fiat improved its offer on Saturday after top German officials said they preferred Magna's initial plan. According to Reuters, Magna has also improved its bid.

GM has until next week to restructure its operations and prove it can be viable without US state aid but the giant carmaker has already admitted that bankruptcy is probable.

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