The paper said up to seven investors had expressed an interest in taking a stake in GM's European business, of which Opel forms the core.
It said Commerzbank, which GM has hired to find a new investor in Opel, could send out the offer memorandum as soon as this week, the sources told the paper.
It reported that the interested investors were said to include several sovereign funds and at least one private equity company based in Asia.
An unidentified senior GM executive told the paper that the company was seeking a firm pledge from an outside investor within a 60-day deadline imposed by the U.S. government to cut costs and streamline operations.
On Monday, a labor leader at Opel confirmed reports that the German federal state of North Rhine-Westphalia had held talks with Abu Dhabi on possibly investing in the unit.
A spokesman for Germany's economic minister added on Monday that the government was in talks with several potential investors in Opel.
(Reporting by Tim Castle; Editing by Jan Dahinten)