Attorneys general from 11 U.S. states and Washington, D.C. have vowed to fight the Trump administration’s rollback of federal automobile fuel efficiency standards, arguing “a clean, efficient, and high-performance vehicle fleet is an essential component” of the U.S. transportation system. They are joined in their pledge by policymakers representing more than 50 cities in 25-plus states.

The letter signed by attorneys general and local officials says the fuel efficiency standards — which call for new cars sold in the U.S. to achieve an average 54.5 miles per gallon by 2025 — “are both necessary and feasible.” The letter points to a 2016 study by the U.S. Environmental Protection Agency (EPA), the Department of Transportation, and the California Air Resources Board that found automakers were already adopting the stricter standards faster and at lower costs than anticipated. “All Americans… deserve to enjoy fuel-efficient, low-emissions cars and light trucks that save money on gas, improve our health, and support American jobs,” the letter says.

The attorneys general who signed the letter, including from New York, Illinois, Iowa, Massachusetts, and Virginia, among others, join California Attorney General Xavier Becerra in fighting the EPA’s rollback, according to Reuters. Becerra has already threatened to sue to protect the standards.

The standards were negotiated by the Obama administration as part of the automobile industry’s bailout in 2011. If implemented, they would have cut oil consumption by 12 billion barrels over the lifetime of new, more efficient cars, and reduced carbon dioxide emissions by 6 billion tons, according to The New York Times.

Revising the standards has been on President Trump’s agenda since his earliest days in office. In March 2017, during a visit to Michigan, he referred to the standards as “industry-killing regulations” that had contributed to a loss of jobs in the U.S. automobile sector (a claim not backed up by data). EPA Administrator Scott Pruitt announced plans to change the fuel efficiency targets on Tuesday, but gave no clear picture of what the new revised standards would look like.