If negotiations are closed ahead of schedule, the union could be open to criticism that it didn't try hard enough to get all it could for its workers, said Kristin Dziczek who heads the labor relations group at the Center for Automotive Research.
"If you put your pencil down early, did you get everything you can get? Or should you go back and check your work," Dziczek asked, the Detroit Free Press reported Saturday.
The issue arose when a source told the newspaper union leaders believe they can wrap up negotiations with GM before the Sept. 14 deadline. It is practically a tradition that the negotiations go beyond the deadline.
Union leaders are arguing that GM -- and Ford Motor Co. -- are making profits and have no grounds on which to ask for concessions this year.
The UAW is looking to restore a cost-of-living adjustment, have GM hire more workers and potentially fold a Delphi parts facility into GM's manufacturing system.
Delphi emerged from bankruptcy in 2009 with GM buying back two Delphi factories in New York, one in Michigan and one in Indiana.
GM now wants to sell the Delphi plants, the newspaper said.
At the same time, Matt Blunt, president of the American Automotive Policy Center, said both sides are aware that soon after a multibillion-dollar taxpayer bailout of GM, an incendiary negotiation session would not play well in Washington, the Free Press said.