BERLIN --- General Motors Co.'s decision to scrap the sale of European subsidiary Opel raised new uncertainty Wednesday over the unit's future, astonishing politicians in Germany and Russia and prompting workers to plan walkouts in protest.

The GM board's unexpected decision to call off the sale to auto parts maker Magna International Inc. and Russian lender Sberbank was a startling end to months of haggling in which Chancellor Angela Merkel and other German leaders had strongly backed the deal.

Now German workers worry GM will make even more cuts to return Opel to profit than Magna would have.

Still, the decision won a cautious welcome from union officials in Britain and Poland, where workers had feared possible cutbacks in a Magna takeover.

GM's decision handed Ms. Merkel's new center-right coalition government an unwelcome test just a week after taking office. German officials swiftly demanded a restructuring plan from Detroit and vowed to recover by Nov. 30 a $2.2 billion bridge loan granted to keep Opel afloat as a buyer was sought.

"We will get the taxpayers' money back," Economy Minister Rainer Bruederle told reporters. "Dealing with employees in this way eight weeks before Christmas is in no way acceptable."

John Smith, GM's chief negotiator for the sale of Opel, said the U.S. automaker would repay the loan "if we're requested to do so" by Germany.

"We've already begun to repay some of the bridge loan," he told reporters in a conference call.

Opel's chief employee representative, Klaus Franz, said workers would start brief work stoppages today.