DETROIT (AP) — A high-profile spat between the United Auto Workers and Stellantis over reopening an Illinois factory complex has made its way into the race for U.S. president and could elicit a strike against the automaker.

In a speech at the Democratic National Convention Monday night, union President Shawn Fain accused the company of reneging on promises to restart a now-closed assembly plant in Belvidere, Illinois, just over an hour northwest of Chicago.

The union won the reopening in contract talks last fall after a six-week strike at multiple factories run by Jeep and Ram maker Stellantis, as well as General Motors, and Ford.

"Let me be clear. Stellantis must keep the promises they made to America in our union contract," Fain told the crowd at the Chicago convention. "The UAW will take whatever action necessary at Stellantis or any other corporation to stand up and hold corporate America accountable," he said, clearly referring to the possibility of a strike.

In a statement Tuesday, Stellantis confirmed that it notified the UAW of plans to delay reopening of Belvidere but said it stands by the commitment and "strongly objects" to union allegations that it's violating terms of the UAW contract.

"The UAW agreed to language that expressly allows the company to modify product investments and employment levels," spokeswoman Jodi Tinson said in the prepared statement. "Therefore the union cannot legally strike over a violation of this letter at this time."

Stellantis said that it is critical that a business case be made for all investments to match market conditions "to ensure the company's future competitiveness and sustainability, which are necessary to preserve U.S. manufacturing jobs."

In a grievance filed with the company, the UAW said Stellantis has said it won't open a parts distribution hub in Belvidere this year, it won't restart metal stamping operations there in 2025, and it doesn't plan to begin producing a midsize truck at the Belvidere plant in 2027.

The delays violate the 2023 contract, the union said, and could last into 2028, after the current agreement expires. "The union demands that the company rescind its decision to push back the above referenced launches and immediately plant for and fund the Belvidere investments," a grievance filed by the union said.

Fain has been sharply critical of Stellantis CEO Carlos Tavares for threatening job cuts as the company's U.S. sales have faltered this year.

U.S.-European automaker Stellantis reported that its net profits fell by half during the first six months of the year largely because of lower sales and restructuring costs.

The carmaker, which was created in 2021 from the merger of Fiat-Chrysler with PSA Peugeot, reported net profits of 5.6 billion euros ($6 billion) in the period, down 48% compared with 11 billion euros in the same period last year. Revenues in the period dropped 14% to 85 billion euros.

Fain, wearing a red T-shirt that said "Trump is a scab. Vote Harris," told the convention that the union won strong contracts and the plant reopening with the support of Vice President Kamala Harris and President Joe Biden.

"Scab" is a derogatory term for workers who cross union picket lines and work during a strike.

A message was left Tuesday seeking comment from the Trump campaign.