By David Shepardson and Joseph White

The United Auto Workers on Saturday expanded its strike at General Motors to include an additional plant in Spring Hill, Tennessee as the union reached a tentative agreement with the second of the Detroit Three automakers.

”We are disappointed by GM’s unnecessary and irresponsible refusal to come to a fair agreement,” UAW President Shawn Fain said in a statement. GM did not immediately comment.

Spring Hill Manufacturing, an assembly and propulsion plant, is the largest GM facility in North America with nearly 4,000 total employees. It builds the Cadillac XT5 and XT6 as well as electric LYRIQ and GMC Acadia

Moments before employees walked out in Tennessee, the UAW said it reached a tentative labor agreement with Chrysler parent Stellantis. It reached a similar deal with Ford Motor on Wednesday.

A strike at Spring Hill could cripple output at all of GM's large pickup operations, greatly increasing the financial pain for the company.

The UAW's walkout at the Arlington, Texas factory that builds Cadillac Escalades and Chevrolet Suburbans is costing $200 million a week, GM said.

The UAW previously struck GM assembly plants in Missouri and Michigan as well as 18 parts distribution warehouses.

(Reporting by David Shepardson and Joseph White; Editing by Cynthia Osterman)