Defense Secretary Chuck Hagel informed Defense Department civilian employees that some 680,000 of them will have to take a total of 11 days off without pay, one per week from July until the fiscal year ends Sep 30.
The number of forced furlough days could possibly be further reduced if savings in other areas can be found, officials said.
The automatic spending cuts are the result of the inability of lawmakers in Congress - where Republicans have a majority in the lower house - and the White House to agree on how to reduce the deficit, which is calculated to reach $642 billion this year and which in recent years has exceeded a trillion dollars.
The daily Politico and other media have calculated that some 140,000 federal government workers at other agencies have already been informed that they will have to take days off without pay.
The Pentagon is the department most affected by the budget cuts, although Hagel managed to reduce the number of furlough days for civilian Defense Department employees from 22 to 11.
The furloughs also affect the White House, where approximately 480 workers in the Office of Management and Budget and in other departments linked to the presidential residence will have to take unpaid days off.