The Obama administration proposed on Wednesday doubling auto fuel efficiency to 54.5 miles per gallon by 2025, a White House energy priority that has come under scrutiny in Congress.

The plan grew out of an uneasy agreement between the administration, automakers and environmental groups to reduce U.S. dependence on oil imports and cut tailpipe emissions.

U.S. auto dealers are working to undo the Obama administration's fuel efficiency agenda, replacing car companies that for years kept such mandates at bay with the help of allies in Congress.

The car industry is facing dramatic new standards that would double efficiency targets to 54 miles per gallon by 2025, under an administration plan unveiled in July and set to be officially proposed in the coming weeks.

The Obama administration will push back the release of the most ambitious proposal ever for automakers to improve fuel efficiency of their passenger cars, sport utility vehicles and pickups.

The U.S. Transportation Department and the Environmental Protection Agency intended to put out the draft plan for model years 2017-25 for industry and public comment by the end of this week.

Airlines that reduce carbon emissions would receive billions in government financing to help pay for aircraft upgrades tied to U.S.