Magna and its Russian partner Sberbank plan to sign a deal for a 55 percent stake in German carmaker Opel next Monday or Tuesday, several sources familiar with the matter told Reuters.

By then, the Canadian auto parts supplier needs to clinch a deal with Opel's influential labor leaders over annual savings of 265 million euros ($387.4 million).

Unions are negotiating with Magna and Opel minority owner General Motors over a restructuring plan that would lead to thousands of job cuts across Europe.

Separately, British Business Secretary Peter Mandelson said on Monday he was prepared to discuss with Opel's new owners support for the carmaker's UK sister brand Vauxhall, noting that representatives from Magna were due in Britain this week.

A union representing workers at Vauxhall has said it feared at least 1,000 jobs could be cut under the takeover by Magna, which has said it plans to eliminate 10,500 jobs in Europe. Roughly 4,000 would be cut in Germany.

The head of the union had called for talks with Magna over the future of the two British plants at Luton in southern England and Ellesmere Port in the northwest.

I hope (Magna's co-CEO Siegfried Wolf) will have good discussions with union leaders, Mandelson told a group of reporters in Tokyo while on a visit to promote business and economic ties with Japan.

They're looking for hard information and strong assurance of the future viability of Vauxhall's plants.

Some countries that are home to Opel plants have urged the European Commission to ensure the deal with Magna does not favor German workers because of 4.5 billion euros in promised aid from Germany.

Mandelson said Magna representatives would also separately meet with the British government to seek financing for a deal.

Earlier this year Britain secured new investment from Toyota Motor Corp to build hybrid vehicles and from Nissan Motor Co to produce batteries for electric cars.

Mandelson said supporting Vauxhall to develop cleaner technology was an option. We've given support in the past to Vauxhall for development of their green car and I'm prepared to consider that further, he said.

Speaking after meeting Nissan Senior Vice President Andy Palmer, Mandelson said he also hoped that Japan's No.3 automaker would consider Britain for the assembly of its zero-emission electric cars, due to be built somewhere in Europe from 2012.

(Reporting by Angelika Gruber in Frankfurt and Chang-Ran Kim in Tokyo; Editing by Hugh Lawson, John Stonestreet)