The agency says ending Saturday mail delivery would save $2 billion each year.
"Whether it happens today, next month or next year, it's likely that postal customers will need to sacrifice at least some of the conveniences they enjoy today," Carper said.
Door-to-door service for new residential and business addresses would cease in a move that would help the agency shift to less costly curbside and cluster box delivery, under the bill. The measure would require the agency to try to convert residential addresses on a voluntary basis from door-to-door service to curbside and cluster box delivery.
The Senate plan includes changes in how pensions and retiree health care costs are calculated in an attempt to stabilize the agency's finances.