Spyker has extended the deadline for its offer to buy Saab, raising hopes that talks with GM are progressing, according to reports.
However, the Swedish government has warned that there is only a "very, very slim" hope of saving Saab.
Spyker had previously given GM until 10pm tonight UK time to consider its latest proposal, but sources have now said that the deadline has been extended indefinitely as negotiations continue.
Unions and Swedish government officials held emergency talks today in Saab's manufacturing hub of Trollhatten to discuss the likely closure of Saab.
Sweden's enterprise minister, Maud Olofsson, said: "We hope, naturally, that even if it is a very, very slim thread of hope, there is a chance of finding some kind of solution to the question of Saab."
The new Spyker offer does not require accelerated approval of a loan from the European Investment Bank, which was a sticking point.
However, GM is said to be reluctant to sell to Spyker on several grounds, chief of which is selling Saab's intellectual property.
It is also not clear which of Saab's shareholders is involved in the deal. Spyker's chief executive, Victor Muller, refused to confirm or deny if it's largest shareholder, the Convers Group, run by a Russian tycoon Alexander Antonov, was involve. However, he did deny that its second largest shareholder, Abu Dhabi sovereign wealth fund Mubadala Development was bidding.
Muller added: "It's very hard to predict the outcome, particularly since GM in principle has taken a decision to shut Saab down."
Unions in Sweden have written an open letter to GM's board demanding that the US company takes offers for Saab more seriously.
The letter, signed by leaders of the metalworkers and engineers unions, accepts the "serious situation" of Saab and acknowledges the threat of closure but said: "We believe that further alternatives should have been given more attention."