General Motors' Opel unit could end up making cars for other manufacturers if Magna International becomes its partner, German media have reported.

Magna itself is a contract vehicle assembler with a plant in Graz, Austria. Customers have included Chrysler, Daimler, BMW and Mini.

If Opel has to reduce output of its own cars, it could offer capacity to carmakers such as Ford or PSA/Peugeot-Citroen, Automobilwoche and Welt am Sonntag reported, according to Reuters.

Magna does not plan to close any Opel factories in Germany but might shut plants in Antwerp, Belgium, and Luton, England, Welt am Sonntag was quoted as saying.

Automobilwoche reportedly said Magna's idea was to establish an 'open platform' that could be used by multiple manufacturers so that model series could be made efficiently throughout their life cycle. The magazine quoted associates of Magna CEO Siegfried Wolf.

The German government's hunt for an Opel partner has come down to Fiat and Magna, reports said.

Magna would take over Opel jointly with Russian automaker GAZ and Russia's top lender, state-run Sberbank, German reports said.

Fiat wants a three-way merger with Chrysler and GM Europe operations, including Opel, Vauxhall and Saab.

German economy minister Karl-Theodor zu Guttenberg has asked the companies present full plans by Wednesday (May 20).

Should General Motors file for bankruptcy in the US at the end of the month before reaching a solution for its Opel/Vauxhall subsidiary in Europe, the German government would press for a trustee arrangement for the company, economy minister zu Guttenberg has said.