German Foreign Minister Frank-Walter Steinmeier phoned GM's chief executive to underscore Germany's expectations for the sale of GM's Opel unit, a newspaper reported on Saturday.
Without citing sources, mass-circulation newspaper Bild said Steinmeier phoned GM's Fritz Henderson on Friday to say that German government financial guarantees would only be available for an investor that was long-term and that would secure jobs.
Steinmeier is also vice chancellor in the current coalition government and the Social Democrat (SPD) party candidate to succeed conservative Chancellor Angela Merkel in elections scheduled for September 27.
The German states where Opel has manufacturing plants and the federal government have expressed a preference for a bid by Canadian auto parts maker Magna , while sources close to the negotiations have said GM likes RHJ International .
Magna wants to expand Opel's full-scale car assembly business and forecasts high growth rates, particularly in Russia, home of its bidding partner, Sberbank .
RHJ aims to shrink production to return Opel to profit and may be open to selling it back to GM at a later date.
One German state premier said a decision on a new start for Opel could come as early as this week, though a member of the German government's Opel Task Force has said the talks between GM and the two competing bidders could drag on longer than expected.
The endgame of the battle for control of Opel will likely be played out in the Opel Trust, which has formally owned 65 percent of the carmaker ever since GM entered bankruptcy in June and must approve any binding deal.
Opel Trust's board is comprised of two GM representatives and two for Germany -- one for the federal government and a delegate for the four states in which Opel has plants. A fifth neutral board member has no vote.