The United Auto Workers union plans to hold strike authorization votes at one or more of its Stellantis local chapters in the coming days, union president Shawn Fain said on Tuesday, which could lead to significant disruptions for the Jeep maker.

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

United Auto Workers union President Shawn Fain said Tuesday the group plans to hold strike authorization votes against Stellantis because the automaker was failing to live up to guarantees it made during a labor deal struck last year.