Magna International has said it expects to complete its takeover of Vauxhall/Opel by September - but the German government has stressed that it is still open to rival bids.
Magna co-chief executive Siegfried Wolf met Opel workers in the carmaker's Ruesselsheim headquarters on Wednesday and vowed to seal a deal rapidly.
"We think that we will be finished in the next four, five weeks and then there's the final signing," Wolf said. "After the signing, all approvals have to be given, and I think that we can expect a closing in September, end-September."
He also confirmed that Carl-Peter Forster, Opel's chairman and GM Europe's president, will continue to lead Opel.
Opel works council head Klaus Franz also added that the future of GM Europe's factories remains uncertain. Those under most threat are Luton in England, Belgium's Antwerp and Bochum in Germany, he said.
While the German government's 1.5 billion Euro (£1.3 billion) in bridge financing to Opel followed the announcement of the preliminary deal between Magna and GM, it has now stressed that rival bidders including Fiat and BAIC could still step in with improved offers.
"The process is still open to all the bidders," said government spokesman Ulrich Wilhelm.
Earlier, a German official told Reuters that representatives from BAIC met members of the government on Tuesday and made clear they would "seriously consider" a more detailed bid if talks with Magna failed.
The German government has an interest in keeping up the pressure on Magna until a deal is closed, in order to ensure that all its demands are met. These include minimising job cuts and factory closures.