But the decision, which the Postal Service says will save $2 billion a year, barely fazed a number of people interviewed at Chicago-area post offices.
"No one really sends letters anymore," said David Braunschweig, 63, who was at the Arlington Heights post office to mail a gift. "Putting away mail (both Saturday and Sunday), it won't kill anyone."
Hammered by competition that includes the Internet, the Postal Service lost nearly $16 billion last year and said doing away with first-class mail on Saturdays is essential to its recovery plan.
"It's an important part of our return to profitability and financial stability," Postmaster General and CEO Patrick Donahoe said at a news conference Wednesday in Washington. "Our financial condition is urgent."
The agency will continue delivering packages and filling post office boxes six days a week, and all offices that already were operating on Saturdays will continue to do so. Package volume is one bright spot for the Postal Service. It's up 14 percent since 2010, which officials attribute to the growth of online commerce.
The end of Saturday delivery would be the biggest change to mail service since the end of twice-daily delivery in the 1950s. Overall mail volume dropped by more than 25 percent from 2006 to 2011, which could explain the shrugs from several Chicago-area postal customers.
"I was accustomed to getting mail on Saturdays, but we will get accustomed to not getting it as well," Rich Klimczak, 74, said outside the Tinley Park post office. "The only thing I would not like to see is (postal workers) losing their jobs."
The move, which would take effect Aug. 5, aims to reduce the postal workforce by at least 20,000 more employees through reassignment and attrition. It would also significantly reduce overtime payments.
Local union officials estimated that 10,000 postal workers will have their workweek reduced because of the move. On Wednesday afternoon, the Chicago branch of the National Association of Letter Carriers called for Donahoe's resignation.
"USPS executives cannot save the Postal Service by tearing it apart," Cliff Guffey, president of the American Postal Workers Union, said in a statement. "These across-the-board cutbacks will weaken the nation's mail system and put it on a path to privatization."
The National Rural Letter Carriers' Association, which has about 1,500 members in the Chicago suburbs, said the elimination of Saturday service puts the Postal Service in a "death spiral."
Although the Postal Service no longer receives taxpayer money, it remains subject to oversight by Congress, which since 1983 has repeatedly passed measures requiring six-day delivery. Donahoe's announcement appeared to be an effort to force action in Congress after comprehensive postal reform legislation stalled last year.
While many members of Congress insist they would have to approve the cutback, Donahoe told reporters that the agency believes it can move forward unilaterally. The current mandate for six-day delivery is part of a government funding measure that expires in late March.
"There's plenty of time in there so if there is some disagreement" with lawmakers, "we can get that resolved," he said.
The divide among lawmakers on the issue does not break cleanly along party lines. Lawmakers who represent rural areas, who tend to be Republicans, generally have opposed service cutbacks. So have those with strong backing from postal labor unions, mostly Democrats.
Last year, the Senate approved a bill that would have allowed the Postal Service to end Saturday delivery after a two-year period to evaluate the potential effects. Similar legislation in the House never came up for a vote.
The Obama administration had included a proposal for five-day mail delivery in its 2013 budget plan. White House officials, however, had said they supported that change only in concert with other reforms. White House spokesman Jay Carney said Wednesday that officials had not yet studied the latest plan.
Sen. Tom Carper, D-Del., the new chairman of the Senate Homeland Security and Governmental Affairs Committee, expressed concern that the Postal Service's unilateral announcement could complicate his plans for overall reform.
However, he added, "It's hard to condemn the postmaster general for moving aggressively to do what he believes he can and must do to keep the lights on."