DETROIT — The United Auto Workers union isn’t adding any factories to those that are now on strike, but its president says more walkouts could begin at any moment.

Until this week the union had been announcing additional factories on Fridays. But UAW President Shawn Fain told workers in a live video appearance that the companies started gaming the system, waiting until Fridays to make progress in bargaining.

“We will be calling out plants when we need to, where we need to, with little notice,” Fain said on Friday morning. “We’re not sticking to one pattern or one system of giving these companies an extra hour or an extra day. They know what needs to happen and they know how to get it done.”

Fain said the union is still bargaining hard with General Motors and Jeep maker Stellantis. But he criticized Ford, which said Thursday that it had reached the limit of how much money it will spend to settle the strike.

“I found a pathetic irony in that statement,” Fain said, adding that it’s workers who have reached their limits by not getting raises for a decade and giving up what he called retirement security.

His statements came four weeks after the union began its walkouts against the Detroit automakers on Sept. 15.

The strikes started with one assembly plant from each company. The union later added 38 parts warehouses at GM and Stellantis, and then one assembly factory each from Ford and GM. The UAW then made a surprise move on Wednesday, escalating the strikes by adding a huge Ford pickup truck and SUV plant in Kentucky.

About 33,700 workers are on strike against the companies. Analysts say parts supply companies, especially smaller ones without a lot of cash reserves, will be squeezed as the strikes go on.

The head of Ford’s combustion engine vehicle unit said Thursday that the company had reached its limit for the amount of money it will spend to reach a deal with the union.

Kumar Galhotra, president of the Ford Blue business unit, told reporters Thursday that the company stretched to get to the offer it now has on the table that includes a 23% pay raise over four years and other benefit increases.

“We have been very clear we are at the limit,” he said on a conference call with reporters. “We risk the ability to invest in the business and profitably grow. And profitable growth is in the best interest of everybody at Ford.”

The company has a set amount of money, but is willing to move dollars around in a way that might fit the union’s needs, Galhotra said, adding that he still thinks it’s possible to reach a deal.

But Fain told workers Friday that the union added the Kentucky plant after Ford presented an economic offer Wednesday with no more money than a proposal from two weeks ago.

“Ford thought they could wait until Friday morning and then just make a better offer. They stopped being interested in reaching a fair deal now and only became interested in gaming our system of announcing strike expansions on Friday,” Fain said. “They thought they figured out the so-called rules of the game. So we changed the rules.”

Fain added that the Kentucky truck plant strike is sending a “very clear message” to Ford — as well as GM and Stellantis.

The union began the strike by targeting a small number of plants from each company rather than have all 146,000 UAW members at the automakers go on strike at the same time.

Last week, the union reported progress in the talks and decided not to add any more plants. This came after GM agreed to bring joint-venture electric vehicle battery factories into the national master contract, almost assuring that the plants will be unionized.

Battery plants are a major point of contention in the negotiations. The UAW wants those plants to be unionized to assure jobs and top wages for workers who will be displaced by the industry’s ongoing transition to electric vehicles.

Galhotra said Ford is trying to figure out the complexities of pulling its joint venture battery factories into the national contract with the UAW. That would match GM and essentially ensure the plants would be union.

Fain told workers that despite the escalation, they are making progress in their quest to get large wage gains, restore cost of living adjustments, get defined benefit pension plans for all workers, end different pay scale tiers around the nation and win job security assurances with promises to build new vehicles in the U.S.