The deal, worth a reported 660 million Euros, could be made binding as early as the end of the month and would see the Chinese company own a 51 per cent stake in Opel, but analysts say that GM will only consider the offer if the Magna deal falls through.
If the deal were to be completed, BAIC would be the main shareholder in both Opel and its British sister brand Vauxhall, leaving GM with 49 percent.
This remaining share would then be divided between Magna International, which would take a 20 per cent stake, and Russian partner Sberbank 35 per cent.
The remaining percentage would be owned by Opel dealers and employees.
Industry watchers still believe Magna's consortium is the front-runner to buy Opel, but GM has said it is taking to other potential buyers for Opel including Belgium-based holding company RHJ International and BAIC, which builds Mercedes-Benz and Hyundai cars in China with analysts pointing out BAIC is keen to expand out of its domestic market.
One source close to BAIC said it entered the process comparatively late because GM was reluctant to involve it in the process at all, as the US carmaker does not want to create additional competition in China from Opel.
Analysts believe the only way Magna's acquisition of Opel would collapse is if Magna withdrew its bid, forcing GM to then negotiate with another bidder like BAIC.
Fiat CEO Sergio Marchionne said on June 29 that his company is still interested in Opel despite Fiat withdrawing its bid in May.
GM can no longer afford to finance Opel and is selling majority control of the carmaker, which also includes plants in Britain, Spain, Belgium and Poland.
Germany, where most Opel plants are located, has provided 1.5 billion euros in finance to keep Opel alive until an outside investor is found.