The heads of Canada's Magna and Russian partner Sberbank will meet their General Motors counterpart on Thursday, a person close to the matter said, as decision time nears on the sale of GM's Opel business.

Automotive group Magna Co-Chief Executive Siegfried Wolf and Sberbank CEO German Gref would hold an informal chat with GM's Fritz Henderson in Detroit, the source said, adding that no negotiations were on the agenda.

The source was confirming a report in Germany's mass-circulation Bild newspaper, which said the meeting aimed to let all the parties get to know each other better.

Germany also firmed up an offer to make 4.5 billion euros ($6.40 billion) in state aid available should GM select Magna, Berlin's preferred partner, as Opel's buyer.

Government spokesman Ulrich Wilhelm told Reuters on Thursday Germany had made the offer to facilitate a solution to the bidding, but that it would continue to work with other countries in which Opel has plants to come up with a joint solution.

Magna and Sberbank are competing for the business against Belgium-based financial investor RHJ International .

Sources close to the deal have told Reuters that GM's board of directors will address the sale of Opel on Friday and aims to recommend one of the suitors.

Trustees who oversee a majority stake in Opel -- which was ringfenced and propped up with German aid in May to avoid being swept into GM's brief bankruptcy -- must approve any decision.

Germany has been championing the Magna group's offer, while some GM executives have praised RHJ's bid.

(Reporting by Angelika Gruber, Eva Kuehnen, and Alexander Ratz; editing by John Stonestreet)