The United Auto Workers is expected to again expand its strike by 10 p.m. Friday if there is not significant progress in negotiations, as the union president, Shawn Fain, accuses General Motors and Stellantis of “enabling” violence against the union members.

Last week, the union expanded the strike to include 38 parts distribution centers at General Motors and Stellantis in addition to the three assembly plants where the strike began. Mr. Fain explained at the time that Ford was “serious about reaching a deal,” so the union did not expand the strike to more Ford plants.

On Friday, Mr. Fain is expected to announce a further escalation of the strike if the union doesn’t think that the employers are trying to make serious progress in negotiations. 

The biggest sticking point has been wages, with companies offering a 20 percent raise and the union demanding a raise closer to 40 percent, which is based on the increase in executive pay at the Big Three over the past few years.

For the past week, there have been about 18,300 union members on strike, around 12.5 percent of the union’s 146,000 members. It’s not known where the union might expand the strike next.

While Ford was exempted from an expansion of the strike last week, the company has since announced it would be pausing construction on the Marshall Electric Vehicle Battery Plant, a move Mr. Fain called “a shameful, barely veiled threat by Ford to cut jobs.” The union supported the plant, which was supposed to create around 2,500 new jobs.

“Closing 65 plants over the last 20 years wasn’t enough for the Big Three, now they want to threaten us with closing plants that aren’t even open yet,” Mr. Fain said in a statement. “We are simply asking for a just transition to electric vehicles, and Ford is instead doubling down on their race to the bottom.”

Ford has not said why it paused construction, but the company told NPR, “There are a number of considerations.” Republicans in Congress have been quick to claim that it was because of their pressure on the company. 

At the facility, Ford planned to use licensed technology from the world’s largest battery manufacturing firm, Amperex Technology Co. Because the project could have been eligible for some tax subsidies, and Republicans like Senator Rubio said on social media that Chinese companies “shouldn’t benefit from American taxpayer subsidies.”

Mr. Fain did, however, spare Ford from a scathing attack on General Motors and Stellantis, who he accused of “enabling” violence against striking union members by non-union contractors crossing the picket line.

So far, there have been two reports of violence against striking union members, one in Michigan and one in Massachusetts, and a report of threats of violence against striking members in California.

In Michigan, five union members at a Flint General Motors plant were hit by a non-union contractor who drove through the picket line as he was leaving the plant. The attacker has not yet been located. Two of the members who were struck were taken to a local hospital in an ambulance.

In a statement, General Motors spokesman Jack Crawley said that “Plant leadership is working closely with local authorities to investigate and understand what happened” and that the company is “committed to the health and safety of all employees.”

General Motors tells the Sun that the contractor was a “third-party housekeeping contractor” employed by a temporary staffing agency, Malace.

General Motors says they have informed Malace that the three employees in the car that struck five union members are no longer allowed on their facilities. They also said that they are cooperating with local authorities in their investigation. Malace did not immediately respond to a request for comment.

According to General Motors, the company has initiated safety talks at locations with a picket line and instructed contractors to contact site security when they cross picket lines.

At Massachusetts, a union member and a state senator were reportedly hit by cars on the picket line at a Stellantis Depot. In California, non-union truck drivers have drawn weapons against union members, though no one was injured, according to reporting by the American Prospect.

In a statement to the Sun, Stellantis accused striking members of “slashing truck tires, jumping on vehicles, following people home and hurling racial slurs at dedicated Stellantis employees who are merely crossing the picket line to do their jobs” and denied having hired any “scabs.”

“We respect our employees’ right to advocate for their position, including their right to peacefully picket,” Stellantis spokeswoman Jodi Tinson tells the Sun. “But the violence must stop.”

There have been other eruptions of violence on the picket line as well, like at Detroit where a man allegedly hurled insults, racial slurs, and objects at members on the picket line on Friday, according to a report by Fox 2 Detroit.

A video then shows the incident descending into a shoving match before the man takes a sign from a striking union member. After the man raises the sign, a group of picketers traded punches with the man. 

After the fight was broken up, the man walked back to his car. Once at his vehicle, his wife is shown throwing an object at the union members. Then, the man reportedly said he had a weapon, after which members intervened again. The man left before police arrived.

“These members and allies are in our thoughts and we condemn this violence that GM and Stellantis are enabling,” Mr. Fain said in a statement.

Neither Ford nor the UAW immediately responded to a request for comment.