President Donald Trump is reportedly “enraged” that Ford, Volkswagen, BMW, and Honda struck a deal with California to steadily reduce the amount of pollution emitted by their new cars, according to The New York Times. The deal directly contradicts (and potentially threatens) one of the cornerstone efforts of his administration: an attempt to roll back even higher standards set by the Environmental Protection Agency under Barack Obama.

Trump reportedly even summoned other automakers — General Motors, Fiat Chrysler, and Toyota — to the White House to pressure them to stick with the administration’s plan, according to The New York Times.

The new deal with California holds those four automakers (and any others who join the pact) to a standard similar to the one Obama’s EPA set. Automakers would have to decrease the overall emissions of their new vehicle fleets until model year 2026, which in turn will make the new cars more fuel efficient. Since other states follow California’s lead on air regulation, the deal has the potential to split the market if the Trump administration enacts a federal rule with lower standards. The New York Times report also names Mercedes-Benz as the next automaker most likely to join the other four in the pact.

Trump tweeted late Wednesday night that Henry Ford is “rolling over” in his grave at the “weakness of current car company executives” for taking the deal with California. In a statement, Ford said it is “proud to lead the way in taking the right actions for the environment while at the same time protecting consumer affordability and the short- and long-term health of the industry.”

Automakers originally lobbied Trump to relax the Obama-era rule, both before and after his inauguration. But instead of simply loosening the regulatory belt, the EPA and the National Highway Traffic Safety Administration ultimately proposed what amounts to a full rollback of the Obama-era rule. The Trump administration’s rule would freeze the increasing fuel efficiency standards at 2020 levels (around 37 miles per gallon) and no longer hold automakers to the ultimate goal, which was an average fuel economy of more than 50 miles per gallon by model year 2025.

The Trump administration built its proposal around the idea that the high Obama-era standards would make new cars more expensive, pushing consumers to either buy older cars or stick with the one they already own. Since older cars are typically less efficient and don’t have the safety features of newer ones, the Trump administration is essentially making a case to trade the environmental gains of the final five years of the Obama rule for potential upfront cost savings and a reduction in crash-related injuries and deaths.

Trump partially laid out this argument in a tweet on Wednesday, saying he is giving “politically correct Automobile Companies” the option of lowering the average price of a car by “more than $3000” in exchange for “[v]ery little impact on the environment.” He also said his administration is trying to make new cars “substantially safer,” a sentiment he echoed later tweets, despite the fact that the rule being written by the EPA and the NHTSA proposal has nothing to do with making new cars safer. He called automotive executives “foolish,” though it’s not explicitly clear if he was referring to the executives of Ford, Volkswagen, BMW, and Honda.

Trump also tweeted that there could be a time where his administration’s rollback is “no longer available” as an option, which could be a nod to the New York Times’ reporting that he’s considered pulling the rollback and focusing the fight on California’s right under the Clean Air Act to set its own air regulations.

Many experts disagree with the Trump administration’s calculations. Some argue any potential savings on the sticker price of new cars would likely be offset by the increased fuel cost over the life of those vehicles, even if gas prices stay low. With less fuel-efficient cars, the rollback could also introduce hundreds of millions of metric tons of CO2 into the air, and increase oil consumption by more than 1 billion barrels, according to the EPA’s own estimates.

“The clean car standards are the most effective policy we have on the books to fight climate change, and the transportation sector is the country’s largest source of the carbon pollution that causes climate change,” nonprofit advocacy group Sierra Club said in a statement Wednesday. “The Trump administration’s push for dirtier, less efficient vehicles would pump more carbon pollution into our air.”

The EPA and the NHTSA are expected to unveil the final version of the rollback the Trump administration has been promising sometime this year, but The New York Times reports that staff members at those agencies are “struggling to assemble a coherent technical and scientific analysis required by law to implement a rule change of this scope.”

Update August 21st, 8:56PM ET: Added new Trump tweets and part of a statement from Ford.