The Trump administration is challenging California over the state's new automotive emissions and fuel economy "framework" agreement with automakers, insisting setting such standards is the federal government's role.

Lawyers at the Environmental Protection Agency and Department of Transportation on Friday sent a letter to the chairman of the California Air Resources Board, following California's July "framework" agreement with Ford, Volkswagen, Honda and BMW to abide by certain new greenhouse gas emissions standards.

"The purpose of this letter is to put California on notice that this framework agreement appears to be inconsistent with federal law," the letter said. "Congress has squarely vested the authority to set fuel economy standards for new motor vehicles, and nationwide standards for GHG vehicle emissions, with the federal government, not with California or any other state."

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"Given the importance Congress placed on the authority of DOT and EPA for motor vehicle fuel economy and nationwide vehicle emissions standards under federal law, we urge you to act immediately to disassociate CARB from the commitments made by the four automakers," the letter added.

California had imposed stricter fuel economy and emissions standards long before July, and some of the state's laws were enacted before the Clean Air Act. Congress granted a waiver to allow California to enact its own standards, and a dozen other states also adopted California's standards.

The varied standards mean automakers have had to make extra effort in either making two types of cars or manufacturing them all in accordance with the higher California standards.

President Trump has pushed for months to weaken Obama-era mileage standards nationwide. Those standards were designed to make cars more fuel efficient and reduce pollution. The administration moves to rescind California's authority are likely to prompt legal battles. When President George W. Bush challenged California's greenhouse gas emissions and mileage-setting ability, California fought it in the courts. The Obama administration subsequently dropped the Bush effort.

The Trump administration has argued that the extra expense to comply with the emissions requirements will raise the price of new cars, making them unaffordable and depriving buyers of new safety technology. Many experts, including former EPA engineers, have challenged the administration's safety assertion.

Mr. Trump has long advocated for the auto industry, and his administration has emphasized that environmental concerns cannot trump economic considerations.

"You know, for too long, there's been this conventional wisdom that you've got to choose between economic growth and environmental protection," Energy Secretary Rick Perry said during a July speech on the environment that avoided any mention of climate change. "That's a false choice, and it's one that you've talked about, Mr. President. It's always been this country, and this country that leads — just like you reminded people last Thursday — the greatness of America, the innovation of America. And the future of this world will rely greatly upon America and this administration."