WASHINGTON — The Trump administration on Thursday broke off talks on vehicle mileage standards with California, increasing the chances of a court battle that threatens to unsettle the auto industry.

The White House, which has proposed freezing the standards, said it would now move unilaterally to finish its own mileage rule later this year “with the goal of promoting safer, cleaner, and more affordable vehicles.”

The administration’s action challenges California’s decades-old authority to set its own, tougher mileage standards. California has used a waiver that Congress granted it under the 1970s Clean Air Act to help deal with its punishing smog. About a dozen states follow California’s mileage standards; that group accounts for about one-third of U.S. auto sales.

Lawmakers and automakers had urged a settlement and warned that different standards could bring years of court battles and raise costs for automakers and consumers.

“The industry requires certainty about future regulatory obligations,” Honda said in a statement. State and federal government rules should aim for “continuous progress” on cutting fossil-fuel emissions and promoting electric vehicles, the automaker added.

It urged the two sides to find middle ground.

California officials and the administration accuse each other of failing to present any acceptable compromise. The dispute comes as President Donald Trump feuds with the Democrat-led state over his proposed U.S.-Mexico border wall and his threats to take back federal money from a high-speed rail project. California has taken a leading role in a 16-state lawsuit against Trump’s declaration of a national emergency to get money for the wall after Congress refused to provide it.

The administration last year proposed freezing mileage standards for cars and light trucks after slightly tougher 2020 levels go into effect. Doing so would scrap an Obama-era rule that would have improved fuel efficiency in 2025 to a fleet average of 36 mpg on the road. The Obama standard would have raised fuel efficiency by 10 mpg over current levels.