DETROIT (Reuters) - The United Auto Workers said on Thursday it was suing General Motors Co over labor contract violations stemming from its alleged use of temporary workers at an Indiana assembly plant, escalating the union’s fight against GM’s plans to possibly close U.S. factories.

FILE PHOTO: Assembled trucks are ready for delivery at GM's Chevrolet Silverado and GMC Sierra pickup truck plant in Fort Wayne, Indiana, U.S., July 25, 2018. REUTERS/John Gress/File Photo

The lawsuit, filed on Wednesday in U.S. District Court in Ohio, was the union’s first counter-move to GM’s decision in late November to put five North American factories on notice for closure. The decision, which affects four U.S. plants including one in Warren, Ohio, drew the condemnation of U.S. President Donald Trump and members of Congress.

The UAW, which will negotiate a new national labor deal with GM this year, has vowed to fight the cuts. The current labor contract was reached in 2015 and expires in September.

The union said there are about 1,000 laid-off hourly employees that have the right to transfer to plants with openings, including almost 700 at the Lordstown plant in Ohio. GM is employing temporary workers at its Fort Wayne Assembly plant rather than transferring workers, the UAW said.

“UAW members negotiated a binding agreement and we expect General Motors to follow the contract they agreed to and GM members ratified,” UAW Vice President Terry Dittes said in a statement.

In December, the UAW sent a letter to GM formally objecting to the decision to end production in 2019 at four U.S. plants, saying it violates commitments made during the contract talks in 2015. “We will use all of our resources to enforce our agreements,” the union said in the letter.

GM said in a statement that it started the process to bring about 50 workers from the Lordstown plant to Indiana late last year and has ongoing talks with the union regarding staffing needs in Fort Wayne. It declined to comment directly on the lawsuit, however.

The No. 1 U.S. automaker has said the fate of the plants that have no future product allocated will be decided in talks with the UAW.

The union said in the lawsuit that on May 31, 2018, it approved GM’s request to use temporary workers at the Indiana plant through the end of August 2018 to support the launch of new full-size pickup trucks.

GM sought to extend that period, and while the UAW agreed it had also pushed for the laid off pool of workers to eventually be hired to fill those openings, the lawsuit said.

GM ultimately lost the union’s permission to use the temporary workers beyond the end of November, according to the lawsuit.

The UAW said many of the 690 Lordstown workers on layoff had applied to transfer to the openings at Fort Wayne. It is asking the court to make any affected workers whole through back wages lost, benefits, relocation costs and seniority credit.