The White House released the final version of its rules to roll back Obama-era auto emissions standards, taking a critical step toward completing what would be President Donald Trump’s most substantial environmental change since taking office as the novel coronavirus pandemic rages.

The rule, called the Safer Affordable Fuel-Efficient (SAFE) Vehicles Rule and written by the Environmental Protection Agency and the Department of Transportation, would lower fuel economy standards for vehicles sold in the United States from 54 miles per gallon by 2025 to 40 miles per gallon.

“By reducing regulatory burdens, thereby reducing regulatory costs, we will get more Americans into new, safer, cleaner vehicles,” EPA Administrator Andrew Wheeler said in a call with reporters Tuesday.

The two-digit change carries 10-digit implications for climate change. Under the new standard, which could be implemented as soon as this spring, the U.S. auto fleet would emit nearly additional 1 billion metric tons of carbon dioxide over their lifespans on the road than they would under the existing rule. That’s nearly the annual emissions of Japan, the world’s fifth-largest source of planet-heating carbon dioxide.

MANDEL NGAN via Getty Images President Donald Trump pats down his hair as he speaks during the Coronavirus Task Force daily briefing on COVID-19 in the Rose Garden.

The Trump administration insisted it was acting on behalf of American car buyers who prefer gas-guzzling sport utility vehicles and pickup trucks to fuel-efficient cars and electric vehicles. The administration argued repeatedly since first proposing the rollback two years ago that the health benefits of decreasing air pollution from the U.S. auto fleet were dwarfed by the harm caused by discouraging the purchase of newer, safer vehicles.

“The benefits of the final SAFE rule outweigh the costs and will result in thousands of lives saved,” Wheeler said Tuesday.

That math did not bear out when the White House first proposed its replacement to the 2012 fuel mileage rule. Yet the administration fought on anyway, dividing the auto industry between a handful of manufacturers who sided with California regulators, who supported keeping the stronger existing standards, and another group that publicly backed federal authorities in their quest to weaken the rules.

In October, the fight took an abrupt turn when the administration backed down, and the Department of Justice abandoned an investigation into the companies that sided with California.

But as the United States became the epicenter of the global pandemic of COVID-19, the respiratory disease caused by the new virus, the White House ramped up its environmental agenda, halting virtually all the EPA’s enforcement of anti-pollution laws and approving new pipelines and mining projects.

“The Trump administration is facing one of the biggest crises in modern history, so while this new rule might offer a bit of regulatory certainty it’s coming at a time of complete economic uncertainty, and seems to be more of an ideological power move than anything else,” said Jessica Caldwell, an analyst at the auto industry consultancy Edmunds.

Environmental groups on Tuesday condemned the administration for continuing to push its pro-polluter agenda as Americans are focused on a rapidly worsening public health crisis.

“Even in the midst of a global pandemic, the Trump Administration continues to jeopardize the health of millions of Americans by weakening air pollution protections,” Heather McTeer Toney, the national field director of Moms Clean Air Force, said in a statement. “These rollbacks are dangerous, and further reveal the true priority of Trump’s EPA: protect polluters at all costs, even if it sacrifices the health of Americans.”

Gina McCarthy, the former EPA administrator during President Barack Obama’s second term and current president of the Natural Resources Defense Council, said the Trump rollback simply “makes no sense.”

“It will harm the air we breathe, stall progress in fighting the climate crisis and increase the cost of driving,” McCarthy said in a statement. “The only winner from this action is the oil industry, which wants us stuck driving dirty gas guzzlers as long as possible.”

Even Obama, who has so far remained mum on his successor’s assault on his regulatory legacy, made a rare public comment on the rollback.

“We’ve seen all too terribly the consequences of those who denied warnings of a pandemic. We can’t afford any more consequences of climate denial,” he tweeted Tuesday morning with a link to a Los Angeles Times news article on the finalized rule. “All of us, especially young people, have to demand better of our government at every level and vote this fall.”

The final rule will undoubtedly be the target of legal challenges.