The General Motors board of directors will discuss the future of Opel in a telephone meeting on Tuesday, two sources familiar with the matter told Reuters.
One source said there was a slim chance the meeting would choose a winner between the European manufacturer's rival suitors, Canadian auto parts maker Magna and Brussels-listed investment firm RHJ.
But it looks increasingly unlikely a decision will be reached ahead of German federal elections on September 27, analysts and officials believe.
A spokeswoman for GM Europe said the company does not comment on the timing of board meetings.
I hope (a deal) will happen before the vote. We are working toward this goal, Chancellor Angela Merkel -- whose government favors Magna's bid -- told Bayerische Runkfunk radio on Tuesday.
But analysts believe Berlin has admitted defeat in its attempt to install Magna, along with Kremlin-backed lender Sberbank, as majority owners of Opel against the will of GM's management and its $50 billion benefactor, the U.S. government.
Some analysts speculate that GM's board is holding off on formally approving management's preferred bidder, RHJ, so as not to cause Merkel political embarrassment in the run-up to the election.
GM initially consented to a Magna deal but gradually retreated from that position after emerging in slimmed-down form from 40 days of bankruptcy protection on July 10.
Nearly 25,000 people are employed at one of Opel's four German plants and four times that number in the country are estimated to have jobs that depend on the carmaker, GM's second largest brand after Chevrolet with an annual output of over 1 million vehicles.
(Reporting by Angelika Gruber and Christiaan Hetzner, additional reporting by the Berlin news bureau; editing by John Stonestreet)