Unpaid time off for many federal civilian defense employees is “almost certain” if Congress and President Obama fail to avert spending reductions, according to a Pentagon official.

“Furloughs are almost certain to occur if sequestration takes effect,” Army Lt. Col. Elizabeth Robbins, a Pentagon spokeswoman, said Monday. “Given notification requirements they won’t happen for many weeks.”

Rolling furloughs of up to one month could ripple throughout the Defense Department’s 800,000 civilian workforce, according to Todd Harrison, a senior fellow at the Center for Budgetary and Strategic Assessments in Washington, D.C. Some employees may have time off work beginning in February.

“Nothing will actually happen right way,” he said in an email to the Dayton Daily News. “It will take several weeks before DoD starts implementing the cuts. Part of the reason for the delay is the DoD is hopeful that even if sequestration goes into effect Congress will turn it off within a few weeks.”

Secretary of Defense Leon Panetta released a Dec. 20 memo telling civilian workers the Pentagon would examine other budget cutting options before imposing furloughs, but didn’t rule out the possibility workers could spend time off the job without pay.

The U.S. Office of Personnel Management has told federal civilian employees to report for work Jan. 2. The president has exempted uniform service members from job cuts because of sequestration.

Without a deal, sequestration would impose nearly $500 billion in across-the-board cuts over a decade on the Department of Defense beginning this month. The U.S. military already faces $487 billion in reductions over 10 years as part of a past deficit reduction plan. The Pentagon has operated under a six-month continuing resolution set to expire in March.

Wright-Patterson Air Force Base has not released details on how the cuts might impact the sprawling installation of key Air Force commands. The base employed more than 29,700 military and civilian employees and had an economic impact of $4.7 billion in 2011, according to the most recent figures available. The 2011 analysis showed 16,576 federal civilian workers and 3,775 contractor and private business employees worked on the Miami Valley base.

The base contributes to nearly 36,000 jobs outside the fence, according to Wright-Patterson.

In addition to a 9.4 percent sequestration cut, the Defense Department would face an additional 3 percent cut this year beginning in mid-January because of spending caps established by the Budget Control Act, Robbins said.

“Accordingly, the services and DoD agencies have been directed to plan for a 12 percent cut from each account,” she said in an email.

How many jobs might be impacted at area defense contractors isn’t known, said G. Scott Coale, director of Dayton area operations at Modern Technology Solutions, Inc. and a former leader of the Dayton Area Defense Contractors Association.

“There’s just a huge amount of uncertainty because I think people don’t understand what the impact is,” said Coale, a former vice commander of the Air Force Research Laboratory at Wright-Patterson. One concern: The reductions would happen in nine months instead of a full year since the first quarter has lapsed, he said.

Sequestration’s effect on defense contractors will be delayed, according to Harrison, of the Center for Strategic and Budgetary Assessments.

“Money that has already been obligated on contracts is exempt from sequestration, but all new contract awards, extensions, options, etc. will be reduced by 10 percent across the board,” he said in an email. “So the reduction in contractor workforce will be more gradual over months and years.”

A study by the George Mason University Center for Regional Analysis has projected Ohio could lose 21,280 defense-related jobs over two fiscal years because of federal spending reductions out of 40,400 jobs lost across all sectors.

“If sequestration were to kick in and enacted the way it is right now, those 20,000 (defense-related) jobs would be very difficult to replace,” U.S. Rep. Steve Austria, R-Beavercreek, said.

The Arlington, Va.-based Aerospace Industries Association commissioned report estimated a loss of nearly 1.1 million defense-related jobs out of 2.1 million lost nationwide.

Michael Gessel, Dayton Development Coalition vice president of federal government programs, said there’s a sense the military will not face the full effect of sequestration, but will confront more cuts beyond what the Pentagon has agreed to absorb.

“Washington observers generally believe that at some point sequestration will be averted but the timing is not at all clear,” he said. “There is a diminishing hope for a solution (in 2012) although there is hope for a stop gap measure but the general thinking is it could take until March before the issue is resolved.”