Correction: A previous version of this article misidentified a lawmaker who supports the move. It is Sen. Tom Coburn (R-Okla.), not Rep. Tom Cole (R-Okla.), who issued a joint statement with Rep. Darrell Issa (R-Calif.) attesting to the legality of the plan and has joined Issa in encouraging the Postal Service to move forward with it. This version has been corrected.

Lawmakers are divided over whether the short-term funding plan that awaits President Obama’s signature would require the U.S. Postal Service to continue Saturday mail distribution.

Postmaster General Patrick R. Donahoe intensified a debate on Capitol Hill when he announced in February that the USPS would drop to five days of mail distribution while maintaining six-day delivery of parcels beginning in August. The move is meant to help the financially struggling agency save about $2 billion a year.

But Congress has required six-day delivery by the Postal Service since 1987, and the passage of the continuing resolution funding bill Thursday maintains that status quo.

Or so some lawmakers assert. Others disagree, saying the Postal Service is in its right to make the change.

The Government Accountability Office said Thursday that the current stopgap budget requires the Postal Service to maintain six-day delivery. GAO counsel said the same rule would apply under the funding plan Congress approved Thursday.

Lawmakers who oppose five-day service applauded the GAO report, saying it proves that the Postal Service must continue delivering mail on Saturdays.

“The same language has been in appropriations bills for 30 years, and we expect the Postal Service to continue complying with the six-day mail delivery mandate,” said Caley Gray, a spokesman for Sen. Frank R. Lautenberg (D-N.J.).

But Rep. Darrell Issa (R-Calif.), who supports the cutback plan, says he’s found a loophole. His office noted on Thursday that the congressional requirement does not specify what the USPS must deliver on Saturdays — meaning parcel delivery might suffice.

“The Postal Service is not eliminating a day of service, but is merely altering what products are delivered on what day,” Issa said in a joint statement with Rep. Tom Coburn (R-Okla.)

Issa and Coburn have encouraged the Postal Service to move forward with its plan to end Saturday mail distribution despite the GAO report and the funding plan Congress approved this week.

Rep. Gerald E. Connolly (D-Va.), who opposes delivery cutbacks, said in a statement that Issa’s interpretation parses the existing law “in a fashion that frustrates both the nature and the purpose.”

The Postal Service disagreed with the GAO decision.

“The status quo is not an option for us,” said USPS spokesman David Partenheimer. “We continue to lose $25 million a day, and we continue to contend with a serious liquidity crisis. The new delivery schedule is among the actions we need to move forward with to return to long-term financial stability and not be a burden to the American taxpayer.”

The GAO said its opinion did not address what types of delivery would meet Congress’s six-day requirement. That may leave an opening for the Postal Service and Issa’s loophole argument.

“We do not consider whether the planned service changes USPS has announced would comport with the provision,” the GAO said.

“We were not looking at whether specific types of mail deliver meet the requirements,” said Edda Perez, a GAO counsel and one of the authors of the report.