The Trump administration is set to formally revoke California's tailpipe waiver under the Clean Air Act on Wednesday, according to a source with knowledge of the change.

The move is a major strike in the ongoing battle between the Trump administration and California over the state’s right to enact more stringent air pollution standards due to its poor air quality.

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It would come as Trump is fundraising in California, a state that has been a hotbed of resistance to his administration where Hillary Clinton Hillary Diane Rodham ClintonBloomberg rolls out M ad buy to boost Biden in Florida Hillicon Valley: Productivity, fatigue, cybersecurity emerge as top concerns amid pandemic | Facebook critics launch alternative oversight board | Google to temporarily bar election ads after polls close Trump pledges to make Juneteenth a federal holiday, designate KKK a terrorist group in pitch to Black voters MORE won more than 4 million more votes than the president in the 2016 election.

The announcement indicates the White House is moving ahead with plans to split its auto emissions rule into two parts, a move seen as a way to speed up the process of finalizing the hotly debated deregulation.

The first section of the rule formally revokes California’s preemption and waiver under the Clean Air Act, according to two sources with knowledge of the regulation.

The rule could be finalized within a week.

Removal of the waiver would affect 13 additional states that also follow California’s clean air rules.

It’s expected to quickly be challenged in court.

The second part of the rule will include a final decision over what fuel efficiency levels to set emissions at starting in 2025. It will be released within a month, according to one of the sources with knowledge of the rulemaking.

It is not yet known which of the eight fuel economy standard alternatives the Trump administration is favoring, though it’s widely expected it will be lower than the Obama era regulation.

“Trump wants the fuel economy rule out as soon as possible and they decided the best way to get something out ASAP is by bifurcating the rule,” said a source with knowledge of the reasoning behind the rule split. “There is an urgency to get the rule out.”

The White House and President Trump Donald John TrumpFederal prosecutor speaks out, says Barr 'has brought shame' on Justice Dept. Former Pence aide: White House staffers discussed Trump refusing to leave office Progressive group buys domain name of Trump's No. 1 Supreme Court pick MORE, in particular, have increasingly lashed out at moves by California to assert its power to regulate auto emissions standards under the Clean Air Act.

Following an announcement in July that the Golden State entered into its own agreement with four automotive manufacturers to set their emissions standards higher than what is likely to be proposed by the Trump administration, the president tweeted: “Henry Ford would be very disappointed if he saw his modern-day descendants wanting to build a much more expensive car, that is far less safe and doesn’t work as well, because execs don’t want to fight California regulators.”

The Environmental Protection Agency (EPA) and Department of Transportation in early September jointly threatened the state with legal action if California doesn’t abandon its agreement.

The EPA did not return multiple requests for comment.

“While the White House clings to the past, automakers and American families embrace cleaner cars. The evidence is irrefutable: today's clean car standards are achievable, science-based, and a boon for hardworking American families and public health," Becerra said in a statement Tuesday.