Postal Service Struggles to Stay Solvent, and Relevant The United States Postal Service has long lived on the financial edge, but it has never been as close to the precipice as it is today: the agency is so low on cash that it will not be able to make a $5.5 billion payment due this month and may have to shut down entirely this winter unless Congress takes emergency action to stabilize its finances. “Our situation is extremely serious,” the postmaster general, Patrick R. Donahoe, said in an interview. “If Congress doesn’t act, we will default.” In recent weeks, Mr. Donahoe has been pushing a series of painful cost-cutting measures to erase the agency’s deficit, which will reach $9.2 billion this fiscal year. They include eliminating Saturday mail delivery, closing up to 3,700 postal locations and laying off 120,000 workers — nearly one-fifth of the agency’s work force — despite a no-layoffs clause in the unions’ Labor represents 80 percent of the agency’s expenses, compared with 53 percent at United Parcel Service and 32 percent at FedEx, its two biggest private competitors. Postal workers also receive more generous health benefits than most other federal employees. “The situation is dire,” said Thomas R. Carper, the Delaware Democrat who is chairman of the Senate subcommittee that oversees the postal service. “If we do nothing, if we don’t react in a smart, appropriate way, the postal service could literally close later this year. That’s not the kind of development we need to inject into a weak, uneven economic recovery.” Missing the $5.5 billion payment due on Sept. 30, intended to finance retirees’ future health care, won’t cause immediate disaster. But sometime early next year, the agency will run out of money to pay its employees and gas up its trucks, officials warn, forcing it to stop delivering the roughly three billion pieces of mail it handles weekly. In some countries, post offices double as banks or sell insurance or cellphones. In the United States, the postal service is barred from entering many areas. Still, the agency is considering ideas, like gaining the right to deliver wine and beer, allowing commercial advertisements on postal trucks and in post offices, doing more “last-mile” deliveries for FedEx and U.P.S. and offering special hand-delivery services for correspondence and transactions for which e-mail is not considered secure enough. But now, faced with what postal officials call “the equivalent of Chapter 11 bankruptcy,” the agency is asking Congress to enact legislation that would overturn the job protections and let it lay off 120,000 workers in addition to trimming 100,000 jobs through attrition.