Postmaster General and CEO Patrick R. Donahoe speaks during a news conference at U.S. Postal Service headquarters on Wednesday Feb. 6, 2013 in Washington. The financially struggling U.S. Postal Service says it will stop delivering mail on Saturdays but continue to disburse packages six days a week. (Jose Luis Magana/AP)

Lawmakers wrestled Thursday with how to address Postmaster General Patrick R. Donahoe’s announcement that the U.S. Postal Service plans to end Saturday mail delivery in August.

Donahoe moved to circumvent Congress’s long-standing resistance to the proposal for five-day delivery, a move the Postal Service thinks will save about $2 billion annually and help ease its financial losses. The agency lost $15.9 billion in the last fiscal year.

The postmaster took advantage of legislators’ own dysfunction over budget matters this week, gambling that lawmakers will not thwart his plan after Congress’s temporary spending measure expires March 27.

The spending plan includes language requiring six-day delivery, but lawmakers have not said whether they will insist on the language in the next spending bill.

It appeared Thursday that the issue was shaping up among lawmakers like the discussions over the automatic spending cuts, known as sequestration, which are set to kick in March 1.

Legislators questioned the legality of Donahoe’s plan and pointed fingers over Congress’s inability last year to achieve comprehensive postal reform, but none outlined a strategy to prevent the Postal Service’s effort.

Senate Majority Leader Harry M. Reid (D-Nev.) said in a statement Thursday that such a drastic policy move requires congressional approval.

“The Postmaster General relied on flawed legal guidance to claim that he can circumvent Congress’s authority,” he said.

Reid also expressed frustration at lawmakers’ failure last year on postal reform. “This unfortunate scenario could have been wholly prevented if the House had passed the Senate’s bipartisan postal reform bill in the last Congress,” he said.

Sen. Susan Collins (R-Maine), who serves on the Senate Appropriations Committee and supported the Senate’s bill last year, said, “The Postal Service’s decision to eliminate Saturday delivery is inconsistent with current law and threatens to further jeopardize its customer base.”

Other Republicans applauded Donahoe.

Rep. Darrel Issa (R-Calif.), chairman of the House Committee on Oversight and Government Reform, which oversees the Postal Service, supports the plan. His office said the Postal Service could legally alter Saturday mail services despite any future provisions Congress might enact to require six-day delivery. “In its announced change, USPS is not eliminating a day of delivery, but rather altering what products are delivered on that day,” a spokesman said.

The Postal Service did not respond to requests for comment Thursday. Although it plans to end Saturday mail delivery, it has said that it will continue delivering packages on Saturdays and that post offices will be open to sell stamps and other materials. Post office boxes will receive mail on Saturdays, but magazines and some newspapers, catalogues and Netflix will not reach homes that day.

Sen. Bernard Sanders (I-Vt.), who opposes Donahoe’s decision, said in an interview Thursday that he would fight any effort to remove the six-day-delivery requirement from the next spending bill. But he stopped short of saying he would vote against an appropriations bill that does not include the mandate.

“The future of the Postal Service is very important, but it has to be looked at in a broader context,” Sanders said.

Last year, the House and Senate produced competing bills to help staunch the Postal Service’s financial losses. The Senate approved legislation that would have delayed five-day mail delivery for two years while trying out other cost-saving tactics, but the House never voted on the measure. A House bill that would have ended Saturday delivery right away never reached the floor.

House Appropriations Chairman Harold Rogers (R-Ky.) said he had no idea what his committee would do about the postal plan.

Said Rep. Steny H. Hoyer (D-Md.): “I think the problem is the will of the Congress has not been expressed. Congress has not acted, and I think that left a vacuum.”