Speaking at a breakfast sponsored by The Christian Science Monitor, CBO Director Douglas Elmendorf said fixing the problem will require fundamental changes.
"U.S. fiscal policy is unsustainable, and unsustainable to an extent that it can't be solved through minor changes," Elmendorf said.
"It's a matter of arithmetic."
Elmendorf said spending on entitlement programs -- Medicare, Medicaid and Social Security -- along with defense programs and interest on the national, will outstrip all other budget items in 10 years if Congress adopts President Barack Obama's proposal to extend most of the 2001 and 2003 tax cuts, the newspaper reported.
"Government would need to make changes in some set of the large programs, large parts of the tax code that we think of as the fundamental parts of the budget," t get the deficit under control.
The CBO has projected the administration's proposal would lead to annual deficits of about $1 trillion for 10 years.