WASHINGTON - According to a Bloomberg News report, U.S. auto and environmental regulators are delaying, past a self-imposed deadline, the release of a final rule requiring automakers to raise the average fuel-economy of their fleets to 54.5 miles per gallon by 2025. President Barack Obama’s administration didn’t say when it will issue the rule, which would take effect for model-year 2017 passenger vehicles sold in the U.S.

“The rule is still undergoing interagency review and we expect that process to be completed soon,” Lynda Tran, a spokeswoman for the U.S. National Highway Traffic Safety Administration, said in an e-mail to Bloomberg.

The rule and other administration actions “will nearly double the efficiency of the vehicles we drive, helping to save families thousands of dollars at the pump, slashing oil consumption and reducing harmful emissions,” Tran said.

NHTSA and the Environmental Protection Agency wrote the rule, which was released as a proposal in November after Obama announced an agreement with automakers in July.