Updated

The Obama administration has asked the military's Joint Chiefs of Staff to cut the Pentagon's budget request for the fiscal year 2010 by more than 10 percent -- about $55 billion -- a senior U.S. defense official tells FOX News.

Last year's defense budget was $512 billion. Service chiefs and planners will be spending the weekend "burning the midnight oil" looking at ways to cut the budget -- looking especially at weapons programs, the defense official said.

Some overall budget figures are expected to be announced Monday.

Obama met Friday at the White House with a small group of military advisers, including Admiral Mike Mullen, chairman of the Joint Chiefs, Gen. James Cartwright, vice chairman, and Gen. Jim Jones, National Security Council chairman.

FOX News' Jennifer Griffin contributed to this report.