Washington ? The decision whether to cut back U.S. mail delivery to five from six days a week was complicated Thursday by a report that suggested the U.S. Postal Service had overstated the savings to be gained by the change.

The U.S. Postal Regulatory Commission on Thursday said it found only $1.7 billion in savings, compared with the Postal Service’s estimate of $3.1 billion. The commission also warned that the Postal Service had underestimated by as much as $386 million annually the loss of revenue that could come by dropping Saturday delivery.

The Postal Service, which anticipates operating at a $238 billion cumulative loss over the next decade, said last year it would pursue a five-day delivery schedule as soon as this year to cut costs. Congress currently mandates six-day delivery and would have to approve any changes.

The commission, which approves postal rates and operates independently of the Postal Service, made no recommendations about dropping a delivery day. Its members were evenly split over the proposal, said Ruth Goldway, the commission chairwoman, who supports maintaining a six-day service schedule.

She also warned that the Postal Service plan does nothing to address what she believes is an inequitable effect on delivery to rural and remote areas.

“It’s really going to be up to the Congress to say whether they think the service cuts and the impact on rural areas, and the questions about how you interpret the law, are enough of a concern to outweigh some of the savings,” Goldway said.

The Postal Service doesn’t receive taxpayer funding, so cuts don’t have an effect on the federal deficit or the national debt. However, the Postal Service anticipates losing $7 billion this fiscal year.