DETROIT (CNN) -- The United Auto Workers will begin presenting its case Friday morning to an arbitrator who will decide the legality of UAW's strike against two General Motors parts plants.
GM used most of Thursday's arbitration hearing to show why it believes the strikes, which have forced the closing of 27 assembly plants and more than 100 other facilities, are illegal.
The arbitration, which began Wednesday in Detroit, will move to Flint, Mich., Friday morning.
General Motors contends that two strikes at its Flint Metals Center and Delphi East Complex in Flint are illegal under the UAW-GM national agreement.
GM contends the union is trying to strike over the allocation of resources and product placement, which are not strikeable under the pact.
The UAW says that health and safety issues at the local level are permissible strike concerns under the agreement.
If Arbitrator Thomas T. Roberts agrees with GM, the automaker is expected to seek an injunction ordering the 9,200 workers back to their jobs.
The strikes, which began June 5 at the Flint Metals Center, have virtually halted GM's North American assembly operations, idling about 192,800 GM workers.