The White House announced Thursday that it is moving ahead on its much-anticipated plan to roll back the fuel economy mandate set by the Obama administration. The move is likely to mean fewer high-efficiency, zero-pollution cars on the road.

The previous guidelines, which were reached during Obama's first term, call for automakers to steadily reach a fleet average of 54.5 miles per gallon by 2025 — though with credits and other modifications, the actual figure is expected to wind up in the low to mid-40 mpg range. Thursday's announcement means the new standard would be frozen at 2020 levels, around 37 mpg.

Acting Environmental Protection Agency chief Andrew Wheeler said the agency also intends to eliminate California’s authority to set its own automotive emissions rules — guidelines that have traditionally been tougher than those put in place by the EPA for the rest of the country.

“We are delivering on President Trump’s promise to the American public that his administration would address and fix the current fuel economy and greenhouse gas emissions standards,” said Wheeler in a statement. “Our proposal aims to strike the right regulatory balance based on the most recent information and create a 50-state solution that will enable more Americans to afford newer, safer vehicles that pollute less.”

House Minority Leader Nancy Pelosi, D-Calif., called the Trump administration's actions a "dangerous assault on clean air and public health in California and across the nation."

"President Trump's illegal and unjust attack on the vital clean air protections set by California and the 12 states that join it will choke our communities with smog," Pelosi said in a statement, promising that her state would "continue to work with automakers to overcome the Trump obstruction to build cleaner, more affordable and safe vehicles for our communities."

During a conference call with reporters, National Highway Traffic Safety Administration Deputy Administrator Heidi King said the mid-term review conducted by the Trump administration concluded the average new vehicle would increase in price by $2,340 by 2025 — with overall costs to the country estimated at $500 million long-term. As a result, the original, 54.5 mpg target would mean more expensive cars that many consumers couldn’t afford to buy.

In turn, EPA Assistant Administrator Bill Wehrum said that would have a “detrimental impact…on highway safety” by delaying the rollout of improved vehicle technology. The two agencies estimate the proposal could reduce U.S. highway fatalities by 1,000 lives annually.

Recently departed EPA Administrator Scott Pruitt outlined the administration’s plans on Corporate Average Fuel Economy, or CAFE, earlier this year, setting in motion a series of public hearings as well as a meeting between Trump and auto industry leaders to discuss a rollback.

Auto industry officials, notably including former Ford CEO Mark Fields, had vocally supported a rollback during meetings with the then-new president in 2017. Facing heavy pressure from consumer lobbying groups, they have largely been silent about a cut in mileage targets in recent months and, in some cases, have even appeared to come out in favor of keeping the Obama-era mileage targets.

Ford CEO Jim Hackett and Chairman Bill Ford recently issued a statement saying, “We support increasing clean car standards through 2025 and are not asking for a rollback.”

But Ford, along with most of the rest of the industry, does want to eliminate the California waiver.

“From the automakers' perspective, they’ll be happy not to deal with CARB,” (the California Air Resources Board that sets emissions targets), said Dave Sargent, the head of automotive research for J.D. Power and Associates. “What they want more than anything is one set of rules. Multiple sets of rules get expensive” to meet, as that can mean designing one model for states following the California rules and another model for the rest of the country.

Environmental groups, as well as California officials, like CARB chief Mary Nichols, have made it clear they intend to fight any plan that would eliminate the Golden State’s rule-making authority and while Nichols had said earlier this year that she was open to discussing a mileage rollback, she was skeptical that it could be justified.

"Our analysis clearly indicates that the car companies are fully capable of meeting the CAFE standards and they are able to do so with great savings for consumers," echoed Jack Gillis, the Consumer Federation of America's director of public affairs.

California not only supports that target but has put in place guidelines setting a minimum number of zero-emissions vehicles that all but the smallest carmakers would have to sell in that state over the coming years. California is already the country’s largest market for what are commonly referred to as ZEVs, but automakers complain it will be tougher to comply in the other states that have adopted the clean-car rules, such as Vermont.

California and 16 other states, along with the District of Columbia, filed a lawsuit on May 2 challenging the planned CAFE rollback. Further legal action is expected to follow now that the administration will attempt to block the California CO2 waiver.