The U-turn has been viewed by some as a sheepish acknowledgment that its attempt to go to a five-day delivery without the direct approval of Congress was probably without legal standing.

Congress recently including language prohibiting the end of Saturday delivery in a Continuing Budget resolution. "The Board believes that Congress has left it with no choice but to delay this implementation at this time " the USPS said in a statement.

"The Board also wants to ensure that customers of the Postal Service are not unduly burdened by ongoing uncertainties and are able to adjust their business plans accordingly."

The USPS board did stress the fact that it was still in favor of the move to five days, adding it would save about $2bn annually and is a necessary part of the larger five-year plan to return the Postal Service to profitability.

"According to numerous polls, this new delivery schedule is widely supported by the American public," it added. "Our new delivery schedule is also supported by the Administration and some members of Congress."

While Donahoe seemed to suggest at last month's National Postal Forum that the end of Saturday delivery was imminent, Arthur Sackler, coordinator of the advocacy group, Coalition for a 21st Century Postal Service, told PrintWeek: "It was incredibly hard to see how they could forge ahead without violating the law — I read their legal justification and found it not terribly strong."

Sackler did however note this doesn't not mean that Congress won't eventually turn around — perhaps as early as this summer when they begin putting together the federal budget appropriations process for the next fiscal year that begins 1 October.

"This battle isn't over, though my hunch is that restriction on ending Saturday delivery will continue (for this year)," he said.

In early February Donahoe publicly said he did not need Congressional approval to end Saturday delivery, citing the fact the government was operating a temporary budget resolution. That move that drew the wrath of some members of Congress who called the attempt "misguided."

But Sackler said Donahoe's standing in Washington, DC remains strong, adding he had not heard anything to indicate that Congress or the White House in unhappy in any way with his attempts to reform the service that lost nearly $16bn last year.