Officials from UAW locals that represent Ford Motor workers also attended Tuesday's GM meeting to find out details of the concessions.
Ford already has reached a deal with the union to cut labor costs, but GM's agreement has far steeper cuts. Ford officials have said they will seek further changes so that its deal with the union is similar to GM's agreement.
General Motors has been trying to overhaul its business so it can keep receiving federal money to stay afloat as it deals with soaring costs and slumping sales. On Friday, the Detroit automaker borrowed $4 billion more from the federal government on top of the $15.4 billion it has already received.
GM plans to announce the closing of 14 more factories as part of its previously announced effort to shutter 16 plants to trim production and cut costs. The moves will lay off 21,000 workers.
Two of the 16 closures have been announced previously: an engine plant in Massena, N.Y., and a parts stamping plant near Grand Rapids, Mich.