WASHINGTON (AP) ― Americans for generations have come to depend on door-to-door mail delivery. But with the U.S. Postal Service facing billions of dollars in annual losses, that service could be virtually finished by 2022 under a proposal being considered in Congress.

Curbside delivery, which includes deliveries to mailboxes at the end of driveways, and cluster box delivery would replace letter carriers walking right up to homes’ front doors ― a scene deeply embedded in movies and other popular culture.

A House committee on Wednesday approved the plan, which is part of broader legislation designed to cut costs at the agency by up to $4.5 billion a year. The Postal Service had a $16 billion loss last year.

The agency, long ago one of the government’s most powerful for the many jobs it had at its disposal across the country, has suffered from competition by private delivery companies.

The volume of mail handled by the Postal Service has decreased steadily as the popularity of email, Facebook and other electronic services has grown. Total mail volume handled by the agency fell to 160 billion pieces last year from its all-time high, 213.1 billion in 2006. Revenue fell to $65.2 billion last budget year, from a high of $74.9 billion in 2008.

The agency has been pursuing a major restructuring. Since 2006, it has reduced annual costs by about $15 billion, cut its workforce by 193,000, or 28 percent, and consolidated more than 200 mail-processing locations.

Mail delivery can be a sensitive subject among some Americans. The service earlier this year backed off its plan to end Saturday mail delivery, something that it has tried repeatedly and unsuccessfully over the past several years to persuade Congress to approve.

About one in three mail customers has to-their-door delivery, said Rep. Darrell Issa, chairman of the House Oversight and Government Reform Committee.

The Postal Service, an independent agency, gets no tax dollars for its day-to-day operations but is subject to congressional control.

About $11.1 billion of last year’s losses were due to payments for future retiree health costs.