The German government called for clarity from General Motors on its long-term plans for Opel should the U.S. carmaker reverse course this week and decide to keep its European business.

'We are keeping Opel' is not a strategy yet, German Deputy Economy Minister Jochen Homann said on the sidelines of an energy conference in Munich on Tuesday.

Frustration with GM is mounting in the German government, which has come out strongly in favor of Canadian automotive group Magna's bid for Opel, which would entail Detroit permanently ceding control over its former subsidiary.

We have laid the groundwork in the direction of Magna, Homann said.

GM's board of directors meets on Tuesday and Wednesday to discuss Opel, its second-largest brand. Berlin wants a decision ahead of the Frankfurt car show starting next week, where Opel will unveil the latest version of its most important model, the Astra compact.

GM in May consented to a Magna deal but gradually retreated from that position after emerging on July 10 in slimmed-down form from 40 days of bankruptcy protection.

Sources have told Reuters some board members want to keep Opel.

Analysts believe GM's board is holding off on formally reaching any decision until after a German election on September 27, which is likely to produce a new center-right government.

This would avoid embarrassing conservative Chancellor Angela Merkel and her left-leaning coalition partners, the Social Democrats, ahead of the vote.

Rival bidder RHJ raised the stakes last week by sweetening its offer for Opel. The Belgian-listed financial group would pay slightly more and need substantially less state aid, letting it return taxpayer money a year sooner than initially estimated.

Homann hoped for clarity by Wednesday, but his boss, Economy Minister Karl-Theodor zu Guttenberg, said Germany would continue to negotiate with GM should the board postpone a decision again.

NEW ASTRA, NEW IMAGE

Separately, Opel's head of marketing and sales told Reuters that the brand had so far escaped not only unscathed but surprisingly better off, thanks in part to a wave of sympathy mainly in Germany for the ongoing plight of the carmaker.

Here in its domestic market, Opel is often seen as a hapless victim of mismanagement at GM, itself now a symbol of the inexorable decline of the once mighty U.S. auto industry.

Without the synergies from a major company like GM, Opel would not exist, GM Europe Vice President Alain Visser said in an interview.

But we think Opel would be helped by a more independent positioning of the brand, regardless of who the shareholder will eventually be, he added.

German assembly line workers, who began wearing yellow T-shirts declaring We are Opel, gave management the idea for a new image campaign to be unveiled at the Frankfurt show.

In an attempt to assure customers they can keep buying new Astras because Opel will survive, Visser's team adapted the message to We live cars, which will run in German to emphasize its roots, replacing the current slogan Discover Opel.

A lot is at stake, with the new generation Astra hitting the market in November. The Astra accounts for roughly half a million unit sales, or more than a third of overall volume.

Everything we sell this year is dependent on production, which is being ramped up. We anticipate sales of 25,000 units (of the new model) this year, he said.

(Reporting by Vera Eckert, Christiaan Hetzner and Angelika Gruber, editing by Will Waterman)