Stellantis fired back at the UAW on Monday as the clash between the two escalates. Stellantis and the union disagree about a plant reopening.

Chrysler parent Stellantis NV (NYSE:STLA) on Monday denied allegations made by United Auto Workers (UAW) President Shawn Fain that the company failed to keep its commitments made to union workers under an agreement reached last year.

Hill’s Ultium plant voted last week to unionize with United Auto Workers. The company, a joint venture from General Motors and LG Energy Solution, approved the union, making the second UAW success in Tennessee this year.