WASHINGTON (AP) — President Donald Trump announced Wednesday that his administration is revoking California’s authority to set auto mileage standards stricter than those issued by federal regulators, a move critics said would result in less fuel-efficient cars that create more planet-warming pollution.

In a tweet, Trump said his action would result in less expensive, safer cars. He also predicted Americans would purchase more new cars, which would result in cleaner air as older models are taken off the roads.

“Many more cars will be produced under the new and uniform standard, meaning significantly more JOBS, JOBS, JOBS! Automakers should seize this opportunity because without this alternative to California, you will be out of business,” Trump tweeted.

U.S. automakers contend that without year-over-year increases in fuel efficiency that align with global market realities their vehicles could be less competitive, potentially resulting in job losses. However, most of the industry favors increases in standards that are less than the Obama-era requirements, saying their consumers are gravitating to SUVs and trucks rather than buying more efficient cars.

Top California officials and environmental groups pledged legal action on Wednesday to stop the rollback, potentially tying up the issue for years in federal courts. The U.S. transportation sector is the nation’s biggest single source of greenhouse gasses.

“You can’t get serious about climate change unless you are serious about vehicle emissions, said California Gov. Gavin Newsom, a Democrat. “This is such a pivotal moment in the history of the climate change debate.”

It’s not clear yet what the Trump administration will propose as its final fuel-efficiency rules, but in the past it has favored freezing Obama-era mileage standards at 2021 levels. Under the Obama administration requirements, the fleet of new vehicles would have to average 30 mpg in real-world driving by 2021, rising to 36 mpg in 2025. Currently the standard is 26 mpg.

Under Trump, the Environmental Protection Agency contends that freezing the fuel economy standards will reduce the average sticker price of new vehicles by about $2,700 by 2025, though that predicted savings is disputed by environmental groups and is more than double the EPA estimates from the prior administration.

Trump’s tweet does not address the money consumers would save at the gas pump if cars got better mileage. A study released by Consumer Reports in August found that the owner of a 2026 vehicle will pay over $3,300 more for gasoline during the life of a vehicle if the standards are frozen at 2021 levels.

Trump’s claim that his proposal would result in a cleaner environment is contrary to his own administration’s estimate that by freezing economy standards U.S. fuel consumption would increase by about 500,000 barrels per day, a 2% to 3% increase. Environmental groups predict even more fuel consumed, resulting in higher pollution.