Opel autoworkers threatened work stoppages across Europe on Wednesday, as Frank Stronach's dream of becoming a full-fledged automaker died with GM's decision not to sell the floundering division.

General Motors announced late Tuesday that it was turning its back on months of negotiations and would keep the Euro division, as the latest numbers showed some hope for vehicle sales.

Stronach, CEO of Ontario's Magna International, had tried to purchase Adam Opel GmbH in hopes of expanding his business to full-fledged manufacturing.

"GM surprisingly decided to hang onto its battered Europeran division, Adam Opel," said BNN's Michael Kane on Wednesday morning. "But the founder of the Canadian autoparts giant Magna International was blase about the news telling an interviewer 'life goes on.'"

Officials in Berlin were angered by the about-face and the German government vowed to recoup the US$2.2 billion it loaned GM to finance the sale.

The deal had the support of both the German government and labour leaders because it provided the best hope of saving jobs in Germany.

Klaus Franz, a top employee representative with Opel, said workers would walk off the job starting Thursday, participating in brief "warning strikes" signalling their displeasure with the shift by GM.

"We won't help shape the way back to General Motors," said Franz.

"Instead, we'll take up our classic function of defending the workers," he said.

The union IG Metall said workers at four plants in Germany would stop work on Thursday and other plants in Europe would follow suit on Friday.

Opel employs more than 25,000 workers in Germany.

The decision by GM's board was the result of an improvement in Europe's business environment and GM's health since it put the division up for sale late last year, GM Chief Executive Fritz Henderson said.

Germany had agreed in September to chip in a total of $4.5 billion (Euros) in aid to help secure the Magna deal.

With files from The Associated Press