The U.S. Postal Service plans to reduce letter delivery from six days per week, to five beginning Aug. 5, while package delivery would continue six days per week.

The financially troubled service is making the move to save money, but is doing it without a congressional blessing.

Without major restructuring, annual operating deficits will increase.

“We believe this (five day delivery) will save us $2 billion a year,” said David Rupert, U.S. Postal Service spokesman in Denver.

“We believe legally we’re able to do this,” Rupert said. “We encourage Congress not to stand in the way of this decision.”

Congress oversees most aspects of the service.

The service’s funding comes from the sale of stamps and other mail-related materials, but it gets a federal appropriation as well.

In their letter, Issa and Coburn said phasing out letter delivery on Saturday was impeded by a 1984 rider carried in law that ties six-day mail delivery to roughly $100 million in reimbursement from the federal government for postal services.

“With the current FY 2013 government funding resolution set to expire at the end of March, we ask that the six-day mail rider be omitted from any subsequent government funding legislation, enabling the Postal Service to implement this necessary reform without impediment,” the letter said.

A 2010 Gallup poll and several newspaper and media surveys show seven out of 10 Americans support five day delivery, a statement from the service said.

Under the plan, mail delivery to street addresses will occur Monday through Friday. Packages will continue to be delivered six days per week, and Saturday delivery will continue for mail addressed to post office boxes. Post offices currently open on Saturdays will remain open, the statement said.

Letter volume has declined in recent years due to the Internet. However, package volume has increased 14 percent since 2010 and is expected to continue growing over the next decade due to the rise in e-commerce, the statement said.

“The Postal Service is advancing an important new approach to delivery that reflects the strong growth of our package business and responds to the financial realities resulting from America’s changing mailing habits,” said Postmaster General Patrick R. Donahoe. “We developed this approach by working with our customers to understand their delivery needs and by identifying creative ways to generate significant cost savings.”

The Postal Service is implementing major restructuring throughout its retail, delivery and mail processing operations. Since 2006, the service has reduced its annual cost base by approximately $15 billion, reduced the size of its career workforce by 193,000 or 28 percent and has consolidated more than 200 mail processing locations, while continuing to deliver record high levels of service to its customers, said the service.

On Wednesday, Powell Postmaster Wendy Trautman said she had no comments about five-day letter delivery.