A senior Pentagon advisory group, in a series of bluntly worded briefings, is warning President-elect Barack Obama that the Defense Department’s current budget is “not sustainable,” and he must scale back or eliminate some of the military’s most prized weapons programs.

The briefings were prepared by the Defense Business Board, an internal management oversight body. It contends that the nation’s recent financial crisis makes it imperative that the Pentagon and Congress slash some of the nation’s most costly and troubled weapons to ensure they can finance the military’s most pressing priorities.

Those include rebuilding ground forces battered by multiple tours to Iraq and Afghanistan and expanding the ranks to wage the war on terrorism.

“Business as usual is no longer an option,” according to one of the internal briefings prepared in late October for the presidential transition, copies of which were provided to the Globe. “The current and future fiscal environments facing the department demand bold action…”

Pentagon insiders and defense budget specialists say the Pentagon has been on a largely unchecked spending spree since 2001 that will prove politically difficult to curtail but nevertheless must be reined in.

Most important quote? “A few cuts here or there won’t do the trick.”