BERLIN: Relief in Europe at GM choosing a buyer for Opel turned on Friday to worries about job cuts and over whether "New Opel" can survive long term, as the EU warned Germany over state aid to the new owners.

Further concerns focused on the involvement of the Russian government in the loss-making new firm, and over whether the agreement announced on Thursday may yet fall apart over what General Motors called "several key issues" remaining.

Under the deal, GM will sell a 55-percent stake in Opel to a consortium owned 50:50 by Canadian auto parts maker Magna and state-owned Russian lender Sberbank. GM will retain 35 percent and employees the rest.

The agreement covers all GM's European operations except Swedish unit Saab, which is likely to be bought by a Swedish company with support from Chinese interests. GM emerged from bankruptcy in July.

The breakthrough was seen as a coup for Germany, where the government under Chancellor Angela Merkel had pressed hard for GM to choose Magna, offering 4.5 billion euros' worth of state aid.

Half of Opel's 50,000 jobs are in Germany, and in a boost for Merkel's chances of winning a second term in elections on September 27, Opel's new owners have pledged to keep open its four main plants in the country.

"I am exceptionally happy about this decision, which is along the lines of what the government wanted," a visibly relieved Merkel said in Berlin on Thursday, as she rushed to unveil the news even before GM.

But with Magna expected to cut 10,000 jobs, elsewhere in Europe there were worries about where Opel's new owners would make the major cuts that analysts say are crucial for long-term survival.

Opel has about 7,000 employees in Spain, 4,700 at Vauxhall in Britain, 5,500 in Belgium, 1,800 in Italy, 1,600 in Austria and 1,500 in France, according to GM Europe's website.

GM vice-president John Smith said in Berlin on Thursday that Opel's new owners were "contemplating" winding down a plant in Antwerp, Belgium, and shifting some production from Spain to Germany.

"We knew the news would be bad for Belgium, now we just have to hope we can get a good pay-off. We don't have any hope, it's finished here," 33-year-old Ali Aycicek, a machinist at the Antwerp plant, told AFP.

In Britain, Vauxhall workers were worried, with one saying: "I'm absolutely devastated, for the simple reason it doesn't secure the long-term future for this place. The morale is low."

In Spain, Finance Minister Elena Salgado said that Madrid was striving to prevent any job losses, while a UGT trade union official in Spain warned of "a major conflict."

One hope for the workers is the European Commission, which warned Berlin on Friday that its aid was illegal if it is conditional on sites staying open in Germany.

European Commission spokesman Johannes Laitenberger said that some member states have already expressed concern, although there had not yet been any formal complaints lodged.

Merkel's government aims to persuade other European governments to contribute to Germany's state aid package.

It is also far from certain that Magna and Sberbank will be able to carve out a place for "New Opel" in a still struggling global auto industry where in Europe and North America too many cars are being made for too few customers.

"The winner today could be the loser tomorrow," analyst Juergen Pieper from Metzler Bank told AFP. "Everyone knows there is enormous over-capacity in the market ... and Opel is by far the weakest player in Europe today."

German mass circulation daily Bild was also sceptical: "Who is going to pay? The German taxpayer ... Germany is carrying all the risk. Opel is not rescued yet by a long shot."

Newspapers also raised concerns about the Kremlin's involvement, with Germany's Frankfurter Allgemeine saying that "no one knows what the Russians are really planning, what extra demands they will have."

Magna and Sberbank want Russian car maker GAZ, owned by billionaire oligarch Oleg Deripaska, to use its plant in the city of Nizhny Novgorod to make Opels for the depressed Russian market.

Russian Prime Minister Vladimir Putin on Friday said that he hoped the deal was "one of the first steps that will take us towards real integration into the European economy."