In a statement, union leaders said they are reviewing what ATI said would be its last, best and final offer, which came with a 10 August deadline for the union negotiators to approve the agreement and recommend it for ratification.  

If it didn't, the company said it would reserve "its right to take lawful action, including a lockout, for the purpose of supporting" its bargaining position, according to the union.

The union said it is discussing the proposal with its membership.  

"After these discussions, we will be better prepared to determine our next step, including whether we will present this offer to the full membership for a vote," the union said in a statement.

The union said it remains committed to negotiating a fair agreement.

"We believe we've made significant progress in these talks and that there is ample opportunity for us to continue to do so. Unfortunately, ATI continues to try to force us into accepting an agreement solely on its terms. We cannot and will not accept the company's recent ultimatum," the union said in a statement.

USW International Vice President Tom Conway, who chairs the union bargaining committee, said in a statement that talks have been productive and hoped that ATI would return to the bargaining table.

"This company would be better served spending more time at the bargaining table working with us on real solutions than  
working against us by setting false deadlines and attempting to divide our membership," he said.