The move, approved by GM's board of directors, drew immediate criticism from Germany, with the country's Economy Minister Rainer Bruederle demanding Wednesday that the U.S. automaker return the 1.5 billion euros in bridge loans the German government provided for Opel to prepare for GM's bankruptcy.

The Big Three carmaker, which filed for Chapter 11 bankruptcy protection in June, said in September it agreed to sell a majority stake in Opel to Canadian auto parts maker Magna International Inc. and Russian lender Sberbank.

But its latest decision reverses the plan, with GM saying it will instead retain Opel and start the process of restructuring its European operations "in earnest," using about 3 billion euros initially.

Germany had provided the bridge loans to GM from the standpoint of maintaining Opel's employment and on condition that GM will sell it.

Meanwhile, Opel workers said Wednesday they will hold a strike in Germany and other parts of Europe possibly on Thursday in protest to GM's decision not to sell the firm.