Sean Fein, president of the United Auto Workers union in the United States, warned that the historic strike at three factories of the "Big Three" auto giants would expand if companies did not raise their offers to raise wages in the ongoing negotiations.
In a statement to CBS, Finn said, "If we don't get better offers to meet the needs of members, we'll step up the action."
He said GM, Ford and Stellantis had "no excuses" for not resolving wage disputes given the big profits they have made in recent years.
"We are ready to do whatever we have to do," he said, adding that members were fed up.
The union's demands include a 40 percent wage increase for the next four years.
But car companies are currently offering a 20 percent increase.
Other sticking points include increased pay and allowances for junior staff to reduce the gap between them and those who are more experienced, who currently receive about $32 an hour.
The strike, now in its third day, has sparked a fierce debate in Washington over President Joe Biden's economic policy and whether he is doing enough to resolve the auto dispute.
About 12700,150 of the <>,<> workers the union represents are taking part in the strike, but Finn's comments suggest the action could be scaled up, with repercussions across all sectors of the U.S. economy.