U.S. Postal Service letter carrier Jamesa Euler delivers mail in the rain in Atlanta in February.

David Goldman/AP

The U.S. Postal Service lost some $16 billion last year and continues to bleed red ink. Congress has been unable to agree on a rescue plan.

The latest proposal would allow the post office to end Saturday delivery in a year and enable it to ship wine and beer.

The Postal Service's woes are familiar: People don't really send letters anymore, so first-class mail is down, and Congress makes the post office prepay future retiree benefits to the tune of $5.5 billion a year.

Democratic Sen. Tom Carper of Delaware says the Postal Service is on the verge of financial collapse.

"The Postal Service can't continue to bleed money, to run up its tab at the Treasury," says Carper, who heads the Senate panel with oversight of the Postal Service. "The Postal Service owes more than $15 billion to the Treasury ? and the ticker's still running."