The Pentagon announced Tuesday that most of its civilian employees will be forced to take 11 furlough days starting in July, spurring angry calls from Republicans for Congress to intervene.

Defense Secretary Chuck Hagel issued a four-page “for official use only” memo outlining the furlough policy, saying he “very reluctantly” is imposing the forced unpaid days on most of the 800,000 civilian employees through the end of fiscal year 2013.

While the Pentagon was able to shorten the number of furlough days from the original 22 to 11, Hagel said they could not be completely avoided because of the “sequestration” budget cuts that started March 1. The $500 billion in decade-long defense spending reductions are projected to tap $37 billion in FY ’13, with $20 billion coming from operation and maintenance accounts that support civilian workers.

“In addition, because our wartime budget is also subject to sequestration, we must utilize funds originally budgeted for other purposes in order to provide our troops at war with every resource they need,” Hagel wrote. “To compound our problems, when we estimated future wartime operating costs more than a year ago, we planned on fuel costs below what we are currently experiencing.”

All those factors led to an operation and maintenance shortfall of more than $30 billion, which Hagel noted exceeds 15 percent of the Pentagon’s budget request.

Hagel told Pentagon employees at a town hall meeting in Alexandria, Va., yesterday that “if we can do better, as we get through the front end of this over the next few months,…then we might be in a position to be able…to knock that back,” referring to the 11 furlough days.

Still, he added: “I can’t promise that. I won’t promise that.”

Pentagon civilian employees will start receiving furlough proposal notices on May 28, and then their actual decision letters dictating their unpaid leave will be sent out starting on June 5. Then furlough periods will start as early as July 8, and force most personnel to take one unpaid leave day a week through the end of September.

Multiple Republican lawmakers said Tuesday that these massive furloughs should force Congress and the White House to soften the blow of the sequestration cuts on the Pentagon.

Senate Armed Services Committee (SASC) member Sen. John McCain (R-Ariz.) told reporters that Congress and the White House should pass a law like the one President Barack Obama signed this month to grant the FAA more flexibility in applying sequestration cuts to prevent delays at airports. Yet McCain was not optimistic that that would happen.

“My colleagues seem to ignore the fact that all of our service chiefs are saying that it will devastate our national security, it may take us 10 or 15 years to recover,” he said. “(But) our priority is air-traffic control, by god, so we don’t have to wait in line too long at an airport.”

He said legislation like the FAA-relief package could allow the Pentagon to move funding around more easily that it can currently by sending Congress requests to reprogram monies in its coffers. But, he said, “nobody seems to care” in Congress about the defense sequestration reductions.

SASC Ranking member James Inhofe (R-Okla.) blamed the Obama administration for the pending furloughs, noting how it did not plan far in advance of the start of the sequestration cuts for how they would impact the defense budget.

Infhofe also noted that he and Sen. Pat Toomey (R-Pa.) introduced legislation earlier this year–that Obama opposed–to give the Pentagon transfer authority to “minimize the necessity and duration of civilian employee furloughs.”

House Armed Services Committee (HASC) Chairman Howard “Buck” McKeon (R-Calif.) reiterated his call yesterday for Obama to avoid sequestration, by finding “a reasonable way to rein in the debt without hurting the economy or compromising our national security.”

Obama and congressional Republicans remain at odds over how to stop sequestration, with GOP lawmakers balking at new taxes.

HASC Ranking Member Adam Smith (D-Wash.), who wants to stop sequestration through a different approach than McKeon does, nonetheless agreed with him that the furlough notice highlights the need for Congress to stop sequestration.

As this committee has said for almost two years, cutting government spending through sequestration will undermine our military readiness and hurt hard-working families,” Smith said.