WASHINGTON »  After weeks of debate and number-crunching, the Defense Department announced plans today to furlough about 680,000 of its civilian employees for 11 days through the end of this fiscal year, allowing only limited exceptions for the military to avoid or reduce the unpaid days off.

Defense Secretary Chuck Hagel, in a memo to the department, called the decision “an unpleasant set of choices” between furloughing workers or cutting training and flight operations.

And during a town hall meeting with about 6,400 department personnel in Northern Virginia, Hagel was direct: “I tried everything. We did everything we could not to get to this day this way. But that’s it. That’s where we are.”

Telling the workers, he was sorry, Hagel said that after repeatedly going over the number, officials could not responsibly cut any deeper into training and other programs that affect the military’s readiness for combat. He added, “We’ll continue to search for ways to do better, but right now I can’t run this institution into the ditch.”

Hagel said that the department will be evaluating the budget situation over time and will try to end the furloughs early if at all possible. But he and other officials also warned that while they will do all they can to avoid furloughs in the next fiscal year, they can’t promise it won’t happen.

The furlough notices are expected to begin going out May 28, and workers will have several days to respond or seek appeals. The unpaid days off would begin no sooner than July 8, according to the memo. Officials said the furloughs will save the department about $1.8 billion.

“I understand that the decision to impose furloughs imposes financial burdens on our valued employees, harms overall morale and corrodes the long-term ability of the department to carry out the national defense mission,” Hagel said in the memo. “I deeply regret this decision.”

Congressionally mandated automatic budget cuts initially forced the Pentagon to warn that the bulk of its 800,000 civilians would be forced to take 22 unpaid days off — one in each of the last 22 weeks of the fiscal year, which ends on Sept. 30. When lawmakers approved a new spending bill at the end of March, they gave the Pentagon greater latitude to find savings, and the furlough days were cut to 14.

Under pressure from military leaders and members of Congress, the Pentagon will allow the Navy to avoid furloughs for tens of thousands of workers at shipyards. Civilians make up the bulk of the workforce at those facilities and are key to keeping production lines going and preventing major backlogs in the repairs of ships and combat vehicles.

Officials expect that civilian intelligence workers in the National Intelligence Program — largely the CIA — will be exempt from furloughs. But civilians funded in the Military Intelligence Program will be subject to the unpaid days off. Those would include workers in military intelligence agencies such as Special Operations Command and the Army, Air Force and Navy intelligence offices.

Other exempt workers include civilians in the war zone and in critical public safety jobs, as well as people whose jobs are not paid for through congressional funding. As an example, some employees may be contractors or people working in facilities that pay for operations out of their earnings — such as some jobs in recreation or foreign military sales. Overall, defense officials say that about 15 percent of the department’s civilian workforce will be exempt from the furloughs.

In addition, officials said that nearly 11,000 Defense Department school staff and teachers will be furloughed for up to five days, in order to avoid any effects on accreditation.

The officials spoke on condition of anonymity because they were not authorized to speak publicly about the decision.

Defense and military officials have been debating for weeks how to divide up the $7.5 billion-plus it now has the authority to shift from lower priority accounts to more vital operations and maintenance programs. While some argued to use the money to reduce or eliminate furlough days, others said it should be directed at other priorities, including flight and combat training and the massive effort to bring tons of equipment out of Afghanistan.

The Defense Department received authority from Congress to shift about $7.5 billion, and officials said the department has been able to identify at least an additional $1 billion that can be moved in smaller increments from other accounts and doesn’t require congressional approval.

Early on, Navy officials said they thought they may get authority to move as much as $750 million into operations and maintenance accounts, and top leaders pressed for the ability to use the money to eliminate the need to furlough any of their 200,000 naval civilians.

Other military and defense leaders, however, argued for a “one team, one fight” process, insisting that all military civilians should be treated the same and given equal days off without pay.

The Air Force and Army also wanted to use some of the money to fund other priorities that more directly impact their ability to give soldiers and airmen the training and equipment they need to fight. The Air Force wants to restart training flights for units that were grounded due to budget cuts, and the Army wants to restore combat training that has been delayed for some of its troops.

The Army, which is the largest service and has been carrying the bulk of the burden for the war in Afghanistan, also is facing massive bills for the removal of equipment from Afghanistan.

Defense officials said it will cost the military $5 billion to $7 billion to get the trucks, armored vehicles and other equipment out of the war zone, and either bring it home, transfer it to other allies or destroy it so that technologies won’t be compromised.

Because the vast majority of the equipment belongs to the Army, service officials made it clear that those expenses would eat up most of the funding and make it difficult to find any money to cut the number of furlough days for its 330,000 civilians.

According to officials, as much as $5 billion of the reprogrammed money may be allocated to the Army, leaving the other services with less than they had wanted.

Navy officials, meanwhile, have said they want to use about $200 million in order to avoid furloughs for about 30,000 shipyard workers. The Navy has argued that furloughing the workers will end up costing the service more than the salary cuts would save. According to a Navy analysis, forcing the workers to take one day a week off for two to three weeks would extend the ship maintenance time and trigger a ripple effect that will create a backlog, delay deployments and force other ships to remain at sea longer, increasing their costs.

The Air Force, meanwhile, has asked for authority to shift $1.8 billion, hoping to pay for three main priorities: the restoration of flight hours, funds for weapons systems and the possible reduction in civilian furloughs. The Air Force expects a $4 billion shortfall in operations and maintenance accounts.