FILE PHOTO: New cars are shown for sale at a Chevrolet dealership in National City, California, U.S., June 30, 2017. REUTERS/Mike Blake/File Photo

WASHINGTON (Reuters) - The top U.S. auto safety official, a key player in efforts by President Donald Trump’s administration to rollback the nation’s vehicle fuel efficiency requirements, will step down at the end of the month, the Transportation Department announced on Monday.

Heidi King, the acting administrator of the National Highway Traffic Safety Administration (NHTSA), was nominated by Trump to head the agency on a permanent basis but was never confirmed by the Senate, which is controlled by the president’s fellow Republicans. King was appointed as deputy NHTSA administrator in 2017.

Her resignation will take effect on Aug. 31 and she will be replaced as deputy administrator and acting head of the agency by James Owens, the department’s deputy general counsel, the department said. Owens also has been involved in the fuel efficiency regulatory effort.

Reports of King’s impending departure surfaced last week.

NHTSA, part of the Transportation Department, oversees auto safety recalls and fuel efficiency regulations.

King was instrumental in the administration’s initiative to draft new fuel efficiency rules through 2026. Rules put in place under Democratic former President Barack Obama called for a fleetwide fuel-efficiency average of 46.7 miles per gallon by 2026, compared with 37 mpg under the administration’s preferred option.

NHTSA and the U.S. Environmental Protection Agency last week submitted the second part of the final regulation to the White House Office of Management and Budget for review. The final rule is expected to be finalized within months.

King said in June that existing fuel efficiency standards have raised the cost of new vehicles and may “discourage consumers from replacing their older car with a newer car that is safer, cleaner and more fuel efficient.”

The final rule is expected to bar California, the nation’s most populous state and a trend-setter on environmental protection initiatives, from establishing its own vehicle emissions rules.