The Trump administration on Wednesday is expected to revoke California’s authority to maintain the strictest automobile emissions standards in the country, creating yet another rift between the state and White House over environmental policy.

The move would upend California’s status as a national leader on air pollution, having long set fuel-efficiency rules that are tighter than the federal government’s and embraced by other states and the auto industry as a whole.

Famously plagued by smoggy skies, California has been allowed to set its own pollution rules because of a waiver originally granted by the federal government in 1970 under the Clean Air Act. But the U.S. Environmental Protection Agency will announce on Wednesday at a private event in Washington, D.C., that it is withdrawing California’s waiver. The announcement was first reported by the New York Times.

The move has been expected since last year when the administration drafted a proposal to relax clean air regulations implemented under President Barack Obama. The White House said then it wanted a single set of fuel standards for the entire nation.

The issue resurfaced more recently when California environmental regulators pursued an end run on the administration’s proposed rollback. The California Air Resources Board said this summer that it had struck a deal with four major automakers to boost fuel-efficiency standards above what the federal government plans to roll out. The Trump administration demanded that California abandon the pact, citing possible violations of antitrust law.

While California has wanted the stricter standards not only to fight dirty air but greenhouse gas emissions, administration officials have called the effort bad policy. They contend that the automakers will face an excessive burden and consumers will see higher car prices.

The EPA did not return requests for comment, though agency Administrator Andrew Wheeler on Tuesday told the National Automobile Dealers Association that he would soon be revisiting the nation’s fuel-economy standards.

Repeal of California’s waiver , once announced, would take effect in 60 days under federal rules, although officials could seek emergency authority to implement it more quickly. Thirteen other states that have adopted California’s emissions standards also would be affected.

California Attorney General Xavier Becerra has already threatened to take legal action if the state’s exemption is revoked.

“We’ll see you in court if you stand in our way,” he said Tuesday in a message aimed at President Trump.

The Clean Air Act, signed by President Richard Nixon, allowed the federal government to grant a waiver authorizing California to set stricter emissions standards. The waiver went unchallenged until 2008, when President George W. Bush’s administration sought to deny a renewal.

That decision never took effect, however. A federal appeals court had not yet ruled on California’s lawsuit when Bush left office in 2009 and was succeeded by Obama, whose EPA renewed the state’s exemption.

In separate legal cases, two federal judges in 2007 rejected auto industry arguments that the federal law pre-empted, or overrode, California emissions rules. And a federal appeals court has found that the Clean Air Act requires the EPA to prove that the state has no need for a waiver, rather than forcing California to prove that it needs one.

A group of scholars at New York University argued in an essay last year that the EPA lacks authority to revoke a state’s waiver before it expires. California’s current waiver, negotiated with the Obama administration in 2013, is due to last until 2026.

A lawsuit by California, and possibly by other states and organizations on either side of the dispute, “is unlikely to resolve before the 2020 election,” said Julia Stein, project director at the Institute on Climate Change and the Environment at UCLA School of Law.

In the meantime, she said, the most important court action will most likely be a ruling by a federal judge on whether to issue a stay, allowing the state to keep its waiver, while the case is pending. That, in turn, would determine the emissions standards automakers will follow in designing 2021 models.

The other factor determining how auto companies will proceed is what comes of the administration’s final plan to weaken fuel-efficiency standards and when it will be rolled out. Until then, the current Obama-era rules remain in place.

The administration last summer proposed freezing the federal fuel standard at 37 miles per gallon in 2020 instead of pushing toward the 2025 target of an average 54.5 miles per gallon for cars and light-duty trucks enacted under Obama. The deal reached between California regulators and Ford, Honda, BMW and Volkswagen in July was to boost fuel efficiency to roughly 50 miles per gallon by model year 2026 regardless of federal policy.

Automobile pollution not only creates smog, which is known to cause respiratory problems, but is a leading driver of atmospheric warming through the emission of carbon dioxide. Revoking California’s authority to set strict emissions rules would be a major blow to the state’s ambitious efforts to address climate change.

Gov. Gavin Newsom was quick to deride the expected action.

“It’s a move that could have devastating consequences for our kids’ health and the air we breathe, if California were to roll over,” Newsom said in a statement. “But we will not — we will fight this latest attempt and defend our clean car standards. California, global markets, and Mother Nature will prevail.”

The Natural Resources Defense Council, a New York-based advocacy group, said the environmental community is also going to stand up for California.

“This would be a huge rollback of climate protection and would hurt every consumer,” said David Doniger, a senior lawyer for the NRDC. “Cleaner, more-efficient cars cost less to own and operate. They might cost a little more off the lot, but you have to pay much less for gas.”

Kurtis Alexander and Bob Egelko are San Francisco Chronicle staff writers. Email: kalexander@sfchronicle.com, begelko@sfchronicle.com Twitter: @kurtisalexander @BobEgelko