Bidders for German carmaker Opel are being pressed to make last-minute changes to their offers ahead of a meeting on Wednesday that could narrow the field of potential investors in the General Motors unit.

German Chancellor Angela Merkel's government has been considering offers for Opel from Italy's Fiat , Canadian auto parts company Magna International and Belgium-listed industrial holding RHJ International .

China's Beijing Automotive Industry Holding Co (BAIC) emerged as a late contender on Tuesday, but it was unclear whether its bid, which came in after an offer deadline set by Berlin, was being seriously considered.

The central thrust of the meeting in the Chancellery is to get as much security for the bridge financing as we can from all parties, the American side and the investors, government spokesman Ulrich Wilhelm said. I don't expect a decision on one preferred bidder.

Juergen Ruettgers, state premier of North Rhine-Westphalia, where Opel has a large production site, said he saw no final decision on the carmaker's fate at the meeting, which starts at 9 p.m. (3 p.m. EDT).

Ruettgers said he expected Opel bidders to make changes to their existing plans for the German carmaker by the afternoon.

Pressure to agree on a partner has grown ahead of a June 1 restructuring deadline for GM set by Washington, which could lead to a Chapter 11 bankruptcy filing by the firm.

Opel's supervisory board decided at an extraordinary meeting to transfer all European factories, sales organizations and some GM assets to the German unit, labor leader Klaus Franz said.

Through the transfer of sites, patents and rights to technology, the new Adam Opel GmbH will be able to enter a partnership with a possible investor debt-free, he said.

EUROPE-WIDE INTEREST

Opel's struggling U.S. parent, which has been kept in operation since the start of the year with $19.4 billion in emergency federal loans, prepared to face the fallout from a failed debt exchange on Wednesday.

GM bondholders had until midnight to trade $27 billion in debt for a 10-percent ownership stake in the reorganized company that U.S. officials have said could emerge from a quick trip through bankruptcy court.

GM planned to detail the results of the debt exchange offer on Wednesday, a spokeswoman said.

German Finance Minister Peer Steinbrueck said bridge financing for Opel of 1.5 billion euros ($2.10 billion) would depend on investors' proposals and whether a deal could be reached on hiving off Opel from its U.S. parent.

Opel has 25,000 workers at four plants in Germany, and the future of the carmaker has become a politically charged subject in the run-up to federal elections in September.

GM will make the final decision on who buys Opel, but Berlin's view is crucial since it is being asked to stump up billions of euros' worth of loan guarantees as part of any deal.

German ministers met in the late morning for preliminary talks on the different offers.

The Financial Times in London reported that Britain's Business Secretary Peter Mandelson was also involved in negotiations, holding talks with the head of GM and GM Europe in an effort to ensure any deal protected two GM-owned plants in Britain.

Belgium's prime minister and the premier of the Flanders region have written to Germany and the European Commission insisting that Opel's future be settled at a European level.

German Economy Minister Karl-Theodor zu Guttenberg said on Tuesday there was no favorite bidder and insolvency remained an option. Last week, ministers said the Magna bid, backed by Russian investors, looked the best of the three, but since then the bidders have improved their offers.

Outside Germany, GM Europe has plants that employ a combined 15,000 staff in Spain, Poland, Belgium and Britain, where cars are sold under the Vauxhall brand.

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.

(Reporting by Dave Graham in Berlin, Angelika Gruber in Frankfurt, Philip Blenkinsop in Brussels; Writing by Kerstin Gehmlich)

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