U.S. President Barack Obama said his administration finalized plans to increase fuel economy standards for passenger vehicles to 54.5 miles per gallon by model year 2025.
Former Massachusetts Gov. Mitt Romney, the Republican candidate for president, issued a statement describing the standards as "extreme."
His campaign said the Obama administration "always forgets to mention" that higher vehicle costs would offset consumer savings at the pump.
National Wildlife Federation President Larry Schweiger, however, said the White House plan as a "win across the board" that would cut carbon pollution and reduce U.S. dependence on foreign oil.
Tom Amontree, executive vice president for America's Natural Gas Alliance, said the standards could open the door for more natural gas vehicles by leveling "the playing field between natural gas vehicles and other alternatively fueled vehicles."
Currents regulation calls for a fuel economy standard of 35.5 mpg by model year 2016. The U.S. Energy Department had said U.S. drivers are driving farther on less gasoline because of improvements in fuel efficiency.
Beijing in 2009 had fuel efficiency standards of 35.8 mpg while Europe requires cars by model year 2016 to get 50 mpg.