General Motors Co. will enter into the latest of a series of alliances in key overseas markets after agreeing to sell control of its German carmaker Adam Opel GmbH.

GM said it was planning to sell 55 percent of Opel to Canada's Magna International Inc. and Sberbank of Russia, the German government's preferred bidders. The U.S. automaker will retain 35 percent, forming a three-way partnership.

"We're very experienced and very successful in collaborative business models," said John Smith, group vice president for business planning and alliances and GM's chief negotiator in the Opel sale. "GM gets its best results today in collaborative agreements and joint ventures."

The U.S. automaker has thrived in its partnerships with Shanghai Automotive Industry Corp. of China and as part of GM Daewoo Automotive & Technology of South Korea. It will undoubtedly benefit from the political connections of a partner such as state-controlled Sberbank.

But such arrangements have drawbacks. GM will no longer fully control its automotive business in crucial growth markets and will have to compromise with partners who may not always share the same interests.

That may be a risk in the Opel deal. It is being largely financed by the German government, which has provided $2.1 billion in bridge loans and is offering $6.4 billion in loan guarantees in exchange for minimal cuts to German jobs.

The Russians seek to gain expertise in car-making, with ailing automaker OAO GAZ Group expected to acquire part or all of Sberbank's 27.5 percent stake. "This looks so complicated," said auto analyst Jürgen Pieper at Bankhaus Metzler in Frankfurt.

Like many financial analysts, he believes Italy's Fiat SpA would have been a better partner for Opel. "This would have been a pretty clear solution," he said.

But Germany's government and unions expected Fiat would cut jobs and production deeply.

Under the Magna-Sberbank deal, Opel is likely to get preferential treatment in Russia, said Tim Urquhart, a London-based analyst at IHS Global Insight.

But, he added, "I don't know if that's going to be enough long term," to make up for Opel's weakness in western Europe.

Opel has been part of GM since 1929 and recently has played a crucial role in developing the architecture for compact and midsize cars for all of GM's brands.

But it is losing money in the cutthroat European market, and the cost of restructuring Opel is estimated at between $3 billion and $4 billion.

GM explored other options, such as keeping Opel or selling a majority stake to Brussels-based industrial holding firm RHJ International SA. But GM said Thursday its board supported a deal with Magna, with whom it had struck a preliminary deal in May.

Some analysts said GM had little choice. "The German government was able to call the shots in the end," Urquhart said. "They're the major source of financing."

Magna and Sberbank will put in $730 million for a combined 55 percent stake in the New Opel.

Magna anticipates that Opel will be profitable in 2011. At that time, it will start repaying loans and expects to have repaid them by 2014.

Under the agreement, Opel and its British Vauxhall operations will remain an integrated part of GM's global product development system, with all players benefiting from economies of scale and an exchange of technology and engineering resources.

For Magna, the deal represents a breakthrough in its effort to become a full-scale automaker. It has produced certain models, such as the BMW X3 small SUV, for its clients, in limited numbers.

GM's Smith praised Magna's "accountability-driven operating model."

Speaking to reporters at Ford Motor Co.'s Wixom plant, Executive Chairman Bill Ford Jr. said, "I believe Magna will be a very good operator for Opel/Vauxhall."

But he echoed concerns raised by other automakers, such as Germany's Volkswagen AG, about Opel's drive to be a full-fledged car manufacturer.

The sale of GM's European units to Magna raises questions about Ford's relationship with the supplier, which is under contract to provide the powertrains for a series of new electric vehicles Ford is developing. "I've talked to them personally about that. For now, we feel very comfortable," Bill Ford said. "They have clearly said they will respect intellectual property, and we believe them."