The United Auto Workers will strike three plants at each of the legacy Detroit carmakers if a new contract isn’t reached before midnight, setting up a potentially costly and protracted showdown over wages and job security.

The union will initially strike a Ford Motor Co. Michigan plant that makes the Bronco SUV, a General Motors Co. factory in Missouri that makes its Chevy Colorado mid-sized pickup and a Stellantis NV plant in Toledo, Ohio, that makes the Jeep Wrangler, UAW President Shawn Fain said in an online address Thursday night.

The strategy is designed to methodically cut production of profitable vehicles while minimizing the impact on the UAW’s strike fund. The union said it will add strike locations depending on how bargaining progresses.

“Tonight, for the first time in our history, we will strike all three of the Big Three at once” if no deal is reached, Fain said.

The UAW’s unusually broad attack comes amid a resurgence of labor activism in the US. Emboldened by tight labor markets and agitated by inflation and new risks shouldered during the pandemic, unionized workers have notched a series of victories in the last year at some of the most prominent US companies, including major railroads and United Parcel Service Inc.

Ford said in a statement late Thursday the union’s latest counterproposal “showed little movement” from its initial demands. It said those would give an extra boost to the cost-competitiveness of non-union rivals such as Tesla Inc. and Toyota Motor Corp.

The union said 12,700 workers at three plants will be part of the initial action. They will get $500 a week from the union in strike pay.

--With assistance from David Welch and Keith Naughton.

(Updates with details on plants targeted starting in second paragraph.)