The United Auto Workers union (UAW) says its talks with General Motors over a new four-year labor contract have turned sour.

In a letter issued to members and viewed by Reuters, UAW vice president in charge of the GM department, Terry Dittes, revealed that UAW made an offer on Saturday to GM that covered wages, signing bonuses, job security, profit sharing, and other issues. GM responded on Sunday with a counteroffer that UAW that was reportedly almost identical to a previously-rejected offer.

“These negotiations have taken a turn for the worse,” he said. “We, in this union, could not be more disappointed with General Motors. The company has shown an unwillingness to fairly compensate … the UAW.”

Also Read: UAW Reportedly Considering No-Confidence Vote Against GM CEO Mary Barra

In a statement, GM responded saying that it is working “around the clock” to negotiate a new contract.

“We continue to negotiate in good faith with very good proposals that benefit employees today and build a stronger future for all of us,” it said.

One of the main issues regarding negotiations relates to GM’s assembly plans for future vehicles. It is reported that the UAW wants the car manufacturer to make commitments about building more vehicles in the United States. GM has previously said that it needs to build select vehicles in other markets to keep costs down.

GM’s initial offer, provided to the UAW before strikes started on September 16, outlined plans to invest more than $7 billion in its U.S. plants over the life of the deal. It also provided “solutions” for its Lordstown, Ohio, and Detroit assembly plants that it has previously said would cease making vehicles.