Auto Workers Union President Sean Finn has urged workers at Ford and General Motors plants in Chicago and Michigan to join the first strike against Detroit's three largest automakers — Ford, General Motors and Stellantis — to raise salaries and improve benefits.

Finn said in a message posted live online earlier Friday: "I call on workers at Ford's assembly plant in Chicago to stand ready and strike, and I call on workers at GM's Delta Town Lansing plant to stand ready and strike."

"Our brave members of these two factories are the new wave of reinforcements in our struggle for record decades."

An official with the Automobile Workers' Union told AFP that the shutdown began at noon ET as scheduled.

In particular, the federation is demanding a 40 percent salary hike over four years, equivalent to what group leaders have benefited from over the past four years.

But automakers are currently offering a 20 percent increase.

The Auto Workers' Union is using the Sept. 15 strike as bargaining chip, putting more pressure on big companies to reach a deal.

With Friday's action, the number of striking Auto Workers Union members in 21 U.S. states has exceeded 25,17, or about <> percent of all members.