Foreign Minister Frank-Walter Steinmeier, who will face Chancellor Angela Merkel in elections this fall, said at least five European countries would need to cooperate to save Opel.

'That is not easy. There is no model for that,' Steinmeier said at the rally.

Some 1,000 workers rallied at another Opel factory in Eisenach. Demonstrations or work stoppages were also planned in Kaiserslautern, as well as at GM's Saab division in Sweden, the Vauxhall division in Britain, and other sites in Austria, France, Spain and Hungary.

Opel's employee council has called for General Motors Corp. to be open to new partners, as well as government support. Analysts have said however that it would be difficult to separate Opel from GM because it is too closely integrated into the company.

Opel employs about 25,000 workers in Germany and builds cars in Belgium, Poland, Portugal and Britain.

GM has announced it would cut 47,000 jobs globally by the end of the year -- 19 percent of its work force -- with jobs outside the U.S. accounting for 26,000 of the reductions. The company has sought some $6 billion in support from foreign governments to help its operations outside of the U.S.

Speaking in Berlin, German Chancellor Angela Merkel said her government will only consider assistance for Opel when it and GM present a 'sustainable company concept' for the future.

'Only then can we consider what kind of (aid is) necessary,' Merkel said.

Last week, Sweden's government rejected a plea for public funding for Saab, which filed for bankruptcy protection.