Opel workers aim to avert closure of a Belgian factory in Antwerp following a takeover by Canadian automotive group Magna (MGa.TO) by shortening working hours there, Opel's labor leader said on Tuesday.

Then we could say that we build an employment bridge until there is a new product, Klaus Franz said on the sidelines of the Frankfurt Motor Show.

Magna and Russian partner Sberbank (SBER03.MM) last week struck a deal to buy a majority stake of Opel from General Motors GM.UL. They plan to cut about 10,500 jobs from Opel's workforce of 50,000, half of whom work in Germany.

All four of Opel's plants in Germany are to stay open, while Antwerp could close. Talks with labor representatives have not yet started, but Franz said they would begin relatively soon.

Right now we don't need the capacity (in Antwerp). But if we say that the Opel brand is to be globalize, there is potential for 170,000 to 200,000 units, Franz said.

Opel Chairman Carl-Peter Forster, meanwhile, warned that restructuring had to be quick and would not be easy.

A reduction of capacity is inevitable. All presented concepts foresee job cuts, which are absolutely necessary. It is important that we ensure that we have the right size for the future, Forster said at the motor show.

Some countries that are home to Opel plants have urged the European Commission to ensure the carmaker's takeover did not favor German workers because of 4.5 billion euros ($6.6 billion) in promised aid from Germany.

The Commission had said on Monday it planned to query Germany over its preference for Magna's bid for Opel over a rival offer by Belgium-based RHJ International (RHJI.BR).

But Magna's co-CEO Siegfried Wolf said on Tuesday he did not expect the European Commission to block the planned takeover.

The whole idea (of the takeover) is based on being economical, and I cannot imagine that somebody is against being economical. It is comprehensible and transparent, Wolf said in Frankfurt.

(Reporting by Angelika Gruber; Writing by Maria Sheahan)