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 delivery.

Postmaster General Patrick Donahoe announced in February that USPS would drop to five days of mail delivery while resuming delivery of parcels six days a week beginning in August.

Since 1987, Congress has enacted legislation requiring six-day delivery by the Postal Service.

The Government Accountability Office issued an opinion on Thursday saying that a provision in the stopgap budget funding the government through March 27 requires USPS to maintain six-day delivery.

But Rep. Darrell Issa (R-Calif.), who supports the Postal Service’s plan, has argued that the requirement applies to delivery in general, but not mail delivery in particular.

Issa and Sen. Tom Coburn (R-Okla.) issued a joint statement on Tuesday saying, “The Postal Service is not eliminating a day of service, but is merely altering what products are delivered on what day.”

The two Republicans have encouraged the Postal Service to move forward with its plan for ending Saturday mail delivery under that apparent loophole.

Lawmakers opposed to delivery cutbacks said on Thursday that the GAO report proves the Postal Service must maintain the status quo.

Rep. Gerry Connolly (D-Va.) said in a statement that Issa’s interpretation parses the existing law “in a fashion that frustrates both the nature and the purpose.”

The GAO made clear that its opinion did not address what types of delivery would meet the six-day requirement. “We do not consider whether the planned service changes USPS has announced would comport with the provision,” the agency said in its report.

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