CHICAGO—In a speech at the Democratic National Convention here Monday night, UAW president Shawn Fain accused Stellantis of reneging on promises to restart a shuttered assembly plant in Belvidere, IL, northwest of Chicago.

Stellantis had pledged to reopen the factory last fall after a six-week strike against Stellantis, 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.

“To ensure the company’s future competitiveness and sustainability, which are necessary to preserve U.S. manufacturing jobs, it is critical that the business case for all investments is aligned with market conditions and our ability to accommodate a wide range of consumer demands,” the company said in the statement. “Therefore, the company confirms it has notified the UAW that plans for Belvidere will be delayed, but firmly stands by its commitment. As always, the company is committed to engaging with the union on a productive, respectful and forward-looking dialogue.

“The company has not violated the commitments made in the…2023 UAW collective bargaining agreement and strongly objects to the union’s accusations. In fact, the UAW agreed to language that expressly allows the company to modify product investments and employment levels. Therefore, the union cannot legally strike over a violation of this letter at this time.”

In a grievance filed with Stellantis, the UAW said the automaker 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. In a statement Tuesday, Fain said Stellantis is dragging out the process so it never has to reopen the plant.

“They really want to kick the can past our contract expiration so they can suddenly cite ‘market conditions’ again and never reopen the plant,” Fain said. “If they go back on this, what else can they go back on?”

After the contracts were approved, President Biden visited Belvidere with Fain to celebrate the plant reopening.

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. Stellantis reported that its net profits fell by half during the first six months of the year.