Washington (CNN) The Environmental Protection Agency is preparing to revoke California's authority to set its own vehicle emission standards, a source familiar with the plans told CNN on Tuesday, the latest move in the Trump administration's ongoing fight with the Golden State and attempts to chip away at former President Barack Obama's environmental legacy.

The source said the change could come as soon as Wednesday. It's yet another escalation in the clash between California and Trump administration. Industry watchers feared that the Trump administration's plan to freeze federal emission standards, a rollback of tightened standards created by the Obama administration, could have led to two auto markets in the US -- one subject to more restrictive California regulations and another linked to significantly less stringent federal standards.

The Trump administration has also made unraveling Obama's environmental legacy a priority. Months after he arrived in office, President Donald Trump announced the US would leave the Paris Climate Agreement and in June he revoked the Clean Power Plan, the key regulation underpinning the US' pledge in the landmark 2015 international agreement. The administration also recently revoked Obama's Waters of the United States rule and has made number of other moves that would allow for increased oil and gas production on public lands.

The source said the Trump administration will find the EPA previously acted unlawfully by granting the state a waiver from the Clean Air Act and allowing it to develop stricter standards than those of the federal government. About a dozen states have adopted California's standards, which are geared toward the larger goal of curbing greenhouse gases.

California has historically been allowed to have stricter emission standards due to the state's unique geography and history of intense air pollution, highlighted by the thick smog that once blanketed Southern California. Revoking the Golden State's ability to set its own standards could stymie the downward trend in California's air pollution.

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