Germany aims to narrow the field of bidders for General Motors unit Opel on Wednesday and reach a deal to provide the carmaker with temporary financing should its U.S. parent file for bankruptcy.

German Chancellor Angela Merkel's government and GM are considering offers for Opel from Italy's Fiat , Canadian auto parts company Magna , Belgium-listed holding RHJ and China's Beijing Automotive Industry Corp (BAIC).

Merkel has called a top-level meeting for Wednesday as pressure builds to find a solution for Opel before an expected bankruptcy filing by GM.

A first round of negotiations was expected to start at 5 p.m. (11 a.m. EDT) with talks lasting into the night.

Government spokesman Thomas Steg told reporters in Berlin that the meeting, which will include senior politicians and representatives from GM and the bidders, was unlikely to decide on a single preferred bidder.

The focus would be on narrowing the field and setting the stage for a separation of Opel assets from its parent -- a move the government says is necessary to shield the Ruesselsheim-based firm from GM creditors while negotiations with bidders continue.

It is much more probable that talks will be continued with at least two investors after today's meeting, spokesman Thomas Steg said.

The bidders were being pressed to make last-minute changes to their offers and take on more financial risks ahead of a meeting on Wednesday.

Germany holds a federal election in September and its politicians want to avoid giving the impression that German taxpayers will shoulder the burden of an Opel rescue.

At the same time, they are reluctant to let Opel fail ahead of the vote because its 25,000 workers and four plants in Germany would then be at risk.

GM is expected to have the final word on who buys Opel, but Berlin will play a crucial role in the decision because it is being asked to cough up billions of euros worth of loan guarantees as part of any deal.

DOUBTS SURROUND ALL BIDS

Fiat has an ambitious plan to fold Opel into a transatlantic car empire that would also include U.S. manufacturer Chrysler.

Magna wants to use Opel to make an aggressive push into the Russian market, where it would target market share of 20 percent in the short-term together with other GM brands like Chevrolet.

RHJ has not provided details of its bid. China's BAIC came in with a late offer on Tuesday.

A source familiar with the situation told Reuters it aimed to turn Opel into a global brand sold in Asia, Latin America and elsewhere, but this could make Opel a direct competitor and threat to GM. [

Doubts surround all of the bids, and government ministers have said insolvency remains an option. Should talks with bidders continue, Germany plans to place Opel with a trustee to shield its patents and technology from GM creditors.

It is considering offering Opel 1.5 billion euros in bridge financing to tide it over until a deal is finalized and wants the bidders to contribute funds.

Volkswagen Chairman Ferdinand Piech told Austrian radio ORF that he saw problems with the bids from Fiat and Magna, which is a supplier for VW.

We wouldn't like it very much if one of our biggest suppliers turned into a competitor, Piech said. And as for Chrysler, Opel and Fiat we are talking about three sick companies. But who knows, sometimes there's a miracle and a deal like this can work.

Excluding Saab, GM Europe employs some 50,000 workers and has car manufacturing plants in Spain, Poland, Belgium and Britain where Opel cars are sold under the Vauxhall brand, as well as engine and parts sites such as Aspern near Vienna.

Sweden's Saab, also part of GM's assets, is being sold separately. It is in the process of selecting a final candidate from a field of three potential partners lining up to buy it.

In London, Prime Minister Gordon Brown's spokesman said the British government had not ruled out contributing funds to ensure a future for Vauxhall.

We are in regular contact with the German government on bridging finance, he said.

The European Commission said on Wednesday it would organize a meeting of EU industry ministers to discuss the sale of Opel.

That came after Belgium's prime minister and the premier of the Flanders region wrote to Germany and the Commission insisting that the carmaker's future be settled at the European level.

(Reporting by Dave Graham in Berlin, Angelika Gruber in Frankfurt, Philip Blenkinsop in Brussels and Boris Groendahl in Vienna; Writing by Noah Barkin; Editing by Andrew Callus)

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