The U.S. Postal Service would like Congress to allow changes to the mail delivery schedule and other reforms to better control costs, but a set of proposals expected to come to a vote Tuesday could place even more restrictions on when, where and how Americans receive their mail.

The Senate plans to vote on dozens of amendments designed to overhaul the Postal Service, by providing nearly $11 billion to fund the buyouts of hundreds of thousands of employees and, eventually, ending six-day-a-week mail delivery.

The proposals could also establish new service standards and revamp how the USPS sets aside money for its retirees.

Unlike most issues under consideration this year on Capitol Hill, overhauling the Postal Service does not break along traditional partisan or ideological lines. Central to the cost-cutting measures are plans to close hundreds of processing facilities and more than 2,000 post offices, an issue that pits lawmakers from smaller, rural states against colleagues from larger, more urban areas, where the proposed closings would have less of an impact.

Lawmakers who normally work closely together — including Sens. Joseph I. Lieberman (I-Conn.) and John McCain (R-Ariz.) — find themselves on opposing sides of the debate.

Lieberman is a sponsor of the bipartisan overhaul bill, but McCain introduced a different version, backed by House Republicans, that would establish a control board to review postal finances. McCain’s plan will be introduced as an amendment to Lieberman’s bill, but the amendment is not expected to pass.

In all, Senate leaders approved 39 amendments to the bill, but aides expect fewer than 20 to eventually earn an up or down vote.

Sen. Thomas R. Carper (D-Del.), who is sponsoring the main bill with Lieberman, has said that Congress needs to stop acting like 535 members of the Postal Service board of directors. “We can solve this problem if we work together to provide the Postal Service with the flexibility and resources it needs to survive in the 21st century,” he said recently.

But there is little flexibility in some of the proposals unveiled by Carper’s colleagues — most of whom are from rural states set to bear the brunt of the planned cutbacks.

A proposal from Sen. Tom Udall (D-N.M.) would require USPS to continue to deliver mail six days a week. But senators also plan to vote on an amendment by Sen. Bob Corker (R-Tenn.) permitting just five days of mail.

Sen. Barbara A. Mikulski (D-Md.) — who is concerned about the fate of a postal distribution center in Easton — wants state governors to certify that the closing of a distribution center will not adversely affect a local economy. That amendment is expected to earn a vote, but a separate amendment to protect the Easton plant is not.

Western lawmakers upset with the Postal Service’s plans to close tiny rural post offices want to bar USPS from closing rural offices for two more years, and then only if the next-nearest post office is no more than 10 miles away.

Sen. Claire McCaskill (D-Mo.) called plans to close rural postal offices “callous, unnecessary and irresponsible.” Sen. Jeff Merkley (D-Ore.) called the plans “devastating and economically idiotic.”

Montana would also suffer from the cutbacks, so Sen. Jon Tester (D-Mont.) wants to cap the salaries of top-earning postal executives at $200,000 — on par with Cabinet secretaries. Top USPS bosses currently earn much more.

“To me, the choice is simple,” Tester said. “If the Postal Service is out of money, painful cuts have to be made, and they need to be made at the top as much as at the bottom.”

Despite concerns about closing post offices in far-flung rural towns, lawmakers appear to agree on curtailing service to at least one neighborhood: Capitol Hill. An amendment by Sen. Rand Paul (R-Ky.) would authorize the closure of tiny post offices located in some congressional office buildings.