German Economy Minister Karl-Theodor zu Guttenberg said Friday that all options are still open for General Motors Corp.'s (GM) German Opel brand, including possible insolvency.

"All options are still under consideration... I very much call for keeping all three [bids] in the talks," zu Guttenberg told Dow Jones Newswires at the sidelines of an event in Berlin.

Separately, zu Guttenberg described Magna International Inc.'s (MGA) bid for Opel as "interesting," but added that some financial details still require clarification as the German state is expected to support the deal with taxpayers' money.

"It is the case that Magna has presented an interesting concept, but also [one] that has drawn up questions. These are all questions that are relevant to taxpayers," he said.

"We must exercise a risk assessment on how big the default risk of guarantees can be. We have to look at this in a very sober way," zu Guttenberg said.

"It is safe to say that which ever concept we might want to pursue, a substantial number of jobs in Europe is at risk," he said.

Regarding a timeframe for a decision, zu Guttenberg said: "We must have made a principle decision next week because in the U.S. they will make a decision regarding starting insolvency procedures" for Opel's parent, GM.

Company Web site: www.opel.com

-By Andrea Thomas and Christoph Rauwald, Dow Jones Newswires; +49 69 29 725 512; christoph.rauwald@dowjones.com