DETROIT (AP) — The United Auto Workers strikes against Detroit’s three automakers that spread to dozens of parts distribution centers one week ago deepened Friday.

UAW President Shawn Fain made the announcement in a Friday morning video address to union members. Additional walkouts are set to begin at noon Friday, at Ford’s Chicago Assembly Plant and at General Motors’ Lansing/Delta Township plant in Michigan.

The expanded walkouts would include about 7,000 more workers, Fain said Friday.

The union has vowed to hit automakers harder if it does not receive what it calls substantially improved contract offers as part of an unprecedented, simultaneous labor campaign against Ford, General Motors and Jeep maker Stellantis.

Progress was reported in talks Thursday night, and in a statement Friday morning, the union left itself room to delay expansion of the strikes. The statement said Fain would announce “whether more workers will stand up and join the ongoing strike” against the automakers. Friday’s announcement kicked off late due to sudden interest in bargaining from the automakers, Fain said.

The automakers’ last known wage offers were around 20% over the life of a four-year contract, a little more than half of what the union has demanded. Other contract improvements, such as cost of living increases, restoration of defined benefit pensions for newly hired workers and an end to tiers of wages within the union are also on the table.

The union went on strike Sept. 15 when it couldn’t reach agreements on new contracts with Ford, General Motors and Jeep maker Stellantis.

It initially targeted one assembly plant from each company. Last week it added 38 parts distribution centers run by GM and Stellantis. Ford was spared the second escalation because talks with the union were progressing.

Fain said Tuesday that negotiations were moving slowly and the union would add facilities to the strike to turn up the pressure on the automakers if needed.

“We’re moving with all three companies still. It’s slower,” Fain said after talking to workers on a picket line near Detroit with President Joe Biden. “It’s bargaining. Some days you feel like you make two steps forward, the next day you take a step back.”

The union has structured its walkout in a way that has allowed the companies keep making pickup trucks and large SUVs, their top-selling and most profitable vehicles. It has shut down assembly plants in Missouri, Ohio and Michigan that make midsize pickup trucks, commercial vans and midsize SUVs, all of which are profitable but don’t make as much money as the larger vehicles.

In the past the union had picked one company as a potential strike target and reached a contract agreement with that company that would serve as a pattern for the others.

But this year Fain introduced a novel strategy of targeting a limited number of facilities at all three automakers, while threatening to add more if the companies do not come up with better offers.

Before Friday, only about 12% of the union’s 146,000 workers at the three automakers are on strike, allowing it to preserve a strike fund that was worth $825 million before Sept. 14.

If all of the union’s auto workers went on strike, the fund would be depleted in less than three months, and that’s without factoring in health care costs.