Union chairman, Mr Stefan Lofven, told Reuters that Spyker has conducted stress tests on the plan after meeting with Spyker CEO, Mr Victor Muller.
"Spyker is anxious for this to become a reality," Mr Lofven said. "From what we can see, this seems serious. They have put in a lot of time and money into this."
Spyker is pressing ahead with efforts to cut a deal for Saab with GM after lodging a new fast-track offer to buy Saab from GM on Sunday.
Speculation of possible backing from a Dutch billionaire fanned the Saab's hopes of an eleventh-hour reprieve.