The move comes just a day after the relationship went ahead strike at the Stellantis truck factory in Sterling Heights, Michigan, north of Detroit.

The additional plants escalate the labor dispute, which is now in its sixth week and has about 46,000 unionized workers out of work. And the rhetoric from both sides shows they remain far apart on a bid for fair wages and benefits, with the company and union standing firm on their positions.

The addition of the Arlington plant, which makes large SUV trucks such as the Cheverolet Tahoe, GMC Yukon and Cadillac Escalade, came just after GM posted strong third-quarter financial results. SUVs are among GM’s most profitable vehicles.

Company on Tuesday generated just over $3 billion in net profit quarter, which is 7% less than a year ago. But the company reported strong demand and pricing for its vehicles.

UAW President Shawn Fain said in a statement that GM exceeded Wall Street’s expectations, but its offer lags behind Ford by maintaining a two-tier wage structure and offering the weakest 401(k) contribution of the three companies at 8%. “It’s time for GM workers and the entire working class to get their fair share,” Fain said.

GM CEO Mary Barra said on Tuesday morning’s earnings conference call that the company had already made a record offer and would not agree to a deal that would jeopardize the company’s future.

The union said the move came just hours after GM reported quarterly earnings and four days after Fain said GM’s latest offer was not big enough.

Barra said GM’s record offer rewards employees but does not threaten the company or UAW jobs. “Accepting unsustainably high costs would jeopardize our future and the jobs of GM team members, and jeopardizing our future is something I will not do,” she said in a statement.

After announcing the strike in Arlington, GM said it was disappointed by the escalation, calling the strike “unnecessary and irresponsible.” The strike hurts employees and will have “negative effects on our dealers, suppliers and the communities that rely on us.”

Car manufacturers have laid off since the start of the strike and blamed departures for the layoffs. And shares of General Motors Co. have fallen more than 13% this year and on Tuesday hit their lowest levels since 2020 amid the pandemic, when the company’s sales growth fell nearly 11%.

Last week, GM made an offer that increased its previous offer by about 25% in total value, the company said.

Thomas Kochan, a professor of labor and employment at the Massachusetts Institute of Technology, said the escalation means negotiations are at a crucial point.

“The pressures to reach an agreement that everyone can live with are enormous for both the company and the union,” he said. “The effects of an extended strike at all three companies and an extension over a long period of time would be profound and have very serious negative effects on the companies and on the workforce.”

The companies, he said, are close to the limits of their bids and the union is close to what it can reasonably expect.

“There comes a time when the two sides in the negotiations have to have very private conversations,” Kochan said. “It’s time for the public rhetoric to stop.”

He said both sides need to test whether an agreement is possible. “They are professional negotiators and should be able to find a point where both sides can live with a new agreement.”