Colorado Attorney General Phil Weiser vowed Tuesday night to challenge the Trump administration’s “unprecedented action” of revoking California’s authority to set its own auto mileage standards.

Colorado is directly affected by the forthcoming directive, given the state’s decision to mirror California’s low-emission vehicle standards. In August, Colorado adopted a zero-emission standard requiring that at least 5% of automakers’ vehicles available for sale by 2023 be electric.

“This action is a direct assault on our system of cooperative federalism and an effort to undermine the role of states in addressing #climatechange,” Weiser wrote on Twitter. “Colorado will be challenging this ‘unprecedented action.’ ”

In revoking California’s ability to set its own vehicle standards, the administration is asserting that only the federal government has the power to regulate greenhouse gas emissions and fuel economy.

Conservative and free-market groups have been asked to attend a formal announcement of the rollback set for Wednesday afternoon at Environmental Protection Agency headquarters in Washington.

The Boulder-based Southwest Energy Efficiency Project released a statement Tuesday saying the Trump administration’s move “would be a direct attack on Colorado’s participation in the Clean Cars Program.”

“The Clean Cars Program requires automakers to build cars that emit less carbon pollution, and to introduce more electric vehicles to Colorado markets,” the statement said.

But Tim Jackson, head of the Colorado Automobile Dealers Association, praised the decision by the Trump administration, saying “it should be up to the federal government to set nationwide emission standards.”

“Multiple, conflicting standards set by states or local jurisdictions are complicated, costly and contradictory,” he said. “Colorado residents can be assured that no longer can unelected bureaucrats appointed by Colorado’s governor cede authority for air quality here to unelected bureaucrats based in Sacramento, California.”

The Trump administration’s move comes after the Justice Department recently opened an antitrust investigation into a deal between California and four automakers for tougher pollution and related mileage requirements than those sought by President Donald Trump. Trump also has sought to relax Obama-era federal mileage standards nationwide, weakening a key effort by his Democratic predecessor to slow climate change.

Top California officials and environmental groups pledged legal action to stop the rollback.

California’s authority to set its own, tougher emissions standards goes back to a waiver issued by Congress during passage of the Clean Air Act in 1970. The state has long pushed automakers to adopt more fuel-efficient passenger vehicles that emit less pollution. A dozen states and the District of Columbia also follow California’s fuel economy standards.

The Associated Press contributed to this report.