Canadian car parts supplier Magna International is currently leading the pack as a buyer for Opel after signing a preliminary memorandum of understanding with its parent company General Motors last May. But the German government, which agreed to supply €1.5 billion in bridge financing to Opel while a deal was finalised, has said that other options are still on the table.

The Germans have encouraged rival bidders, such as RHJ, China's Beijing Automotive (BAIC) and Italy's Fiat, to return with improved offers, raising the pressure on Magna. Some newspaper sources claim to have seen a document in which BAIC has drafted a plan to use Opel's brand and technology on the Chinese market.

Magna, meanwhile, has pressed ahead with talks on securing a framework deal with General Motors, which last week bounced back from bankruptcy. The head of Magna's European arm told a German newspaper that his company was on track to reach an agreement.

But the Magna bid would burden the German government with €4.4 billion in guarantees against RHJ's €3.8 billion. Magna also plans to close down more plants than RHJ.