Stellantis NV is suing the United Auto Workers to prevent a possible strike stemming from a dispute about promised investments at its U.S. assembly plants.

The United Auto Workers will ask members to greenlight a strike against Stellantis NV, escalating an already tense standoff with one of the world’s largest car manufacturers.

DETROIT — Jeep and Ram maker Stellantis will spend $406 million retooling three Michigan factories so they can build electric vehicles or battery parts.

One sentence in a contract document that runs more than 300 pages is drawing scrutiny as the United Auto Workers warns it could strike Stellantis NV.

United Auto Workers members ratified a four-year labor deal with Daimler Truck North America covering 7,400 mostly Freightliner employees, the union said May 4.

Daimler Truck North America inked a tentative four-year labor agreement with the UAW on April 26, hours before the prior deal at Freightliner manufacturing sites in the U.S. was set to expire.

Around 1,500 unionized employees at Allison Transmission Holdings on Jan. 16 ratified a revised four-year labor agreement, the United Auto Workers union Local 933 said Jan. 17.

Some 1,500 unionized employees at Allison Transmission Holdings are set to vote Jan. 16 on ratifying a revised labor agreement, the United Auto Workers union Local 933 said.

Tesla Inc. notified workers at its California car plant of pay increases across its U.S. factories, the latest bump by a nonunion automaker the United Auto Workers is trying to organize.

Some 1,500 Allison Transmission Holdings employees rejected a deal the company struck with union negotiators, but will remain on the job while talks continue, the company said Dec. 1.