The U.S. Postal Service may need an enormous taxpayer bailout if Congress stymies its bid to end Saturday mail delivery and make other changes to other operations and employee benefits, Postmaster General Pat Donahoe told a Senate panel Wednesday.

The agency “cannot continue on its current path,” Donahoe said at a hearing of the Senate Homeland Security and Governmental Affairs Committee. “Do the right thing. Be responsible.”

Donahoe quickly faced sharp questions from lawmakers worried about the impact on rural service and skeptical of the Postal Service’s authority to override a long-standing congressional ban on reducing delivery days.

“If we’re going to have mail delivery that’s going to work for urban areas, it damn well better work for rural America, too,” Sen. Jon Tester, D-Mont., said.

When asked by Sen. Mark Pryor, D-Ark., to explain the legal justification for five-day delivery, Donahoe did not answer directly, but said the Postal Service had given Pryor’s staff a nine-page opinion. A USPS spokesman later said that the agency would not make the document public.