F1 boss Bernie Ecclestone and investment company Genii Capital are reported to be gathering finance to prove to GM they can fund the purchase of Saab.
Swedish daily newspaper Dagens Industri reports that Ecclestone and Genii are depositing '500 million to one billion' crowns (£56m to £112m) in an account, in order to convince GM that their bid for Saab is serious.
"I have had contacts with GM, who have given us a deadline of the beginning of this week, which I interpret as Monday through Wednesday," Genii spokesman Lars Carlstrom said.
Carlstrom added that, in addition to the cash sum, a buyer must be able to show it doesn't need a loan from the European Investment Bank.
"That is an absolute condition from GM's side and one of the keys to being able to buy Saab," Carlstrom said. "No one knows if the EIB would agree such a loan."
Reports suggest GM wants potential buyers to demonstrate they have £1.1bn to invest in Saab in the long-term, including £125-£250m in cash for immediate investment.
However, it remains uncertain that GM will sell Saab, with a GM Europe source telling Autocar at the weekend that the company had already booked shipping to transport tooling for the new Saab 9-5 to its Buick production facility in China.