It’s safe to say that the last thing the Trump White House expected was for automakers to reject watered-down air-pollution regulations.

But it happened, and President Trump is said to be “enraged,” according to the New York Times.

Ford, Honda, Volkswagen and BMW cut a deal with California last month to abide by the state’s stringent emissions rules, ignoring the federal government’s. And Mercedes-Benz will soon join the agreement, “according to two people familiar with the German company’s plans,” the Times said Tuesday.

A sixth big automaker — one of three recently hectored by the White House — plans to disregard Trump’s proposal and stick to the current, stricter federal emissions standards for at least the next four years, the Times says, citing “executives at the company.”

I don’t think there is any precedent for a major industry to say, ‘We are prepared to have a stronger regulation,’ and to have the White House say, ‘No, we know better,’” said William Reilly, EPA chief in the George H.W. Bush administration.

General Motors, Toyota and Fiat Chrysler were “summoned by a senior Trump adviser to a White House meeting last month where he pressed them to stand by the president’s own initiative, according to four people familiar with the talks,” the Times says.

The six car makers expected to go with the California plan account for about 40 percent of all cars and trucks sold in the U.S. California officials say they expect more automakers to join in the deal.

As with many of Trump’s regulation rollbacks, the auto-emissions plan is aimed at crushing his predecessor’s accomplishments. But that’s threatened by possible expansion of the California deal.

The administration’s efforts to weaken the Obama-era pollution rules could be rendered irrelevant if too many automakers join California before the Trump plan can be put into effect. That could imperil one of Mr. Trump’s most far-reaching rollbacks of climate-change policies,” the Times says.

Trump’s plan “would significantly weaken the 2012 vehicle pollution standards put in place by … Obama, which remain the single largest policy enacted by the United States to reduce planet-warming carbon dioxide emissions,” the Times says, requiring automakers to “nearly double the average fuel economy of new cars and trucks to 54.5 miles per gallon by 2015.”

Trump’s proposal would freeze mileage standards at about 37 mpg.

The main reason some automakers have balked at Trump’s proposal is that California and 13 other states plan to continue enforcing their own stricter rules, and to sue the Trump administration.

“That could lead to a nightmare situation for automakers: Years of regulatory uncertainty and a United States auto market … effectively split,” says the Times.

There’s division within the administration, as well, the Times notes: “three senior political officials working on the rollback … have all left the administration recently. A senior career official with years of experience on vehicle pollution policy was transferred to another office.”

As a result, the complex new rules are being written by a team directed by “a 29-year-old White House aide with limited experience in climate change policy,” the Times says, adding that it’s unlikely the revised regulations can be finished before October.