President Bush's five-year defense plan is at least $100 billion shy of the funds needed to carry it out, according to the General Accounting Office.

About half the shortfall stems from unrealistically low assumptions about the future rate of inflation, the congressional watchdog agency told the House Armed Services Committee.The report, which was scheduled to be released Wednesday, was described by sources who declined to be identified.

The GAO study involves the five-year Pentagon budget, which is updated annually and forms the basis for future Defense Department budget decisions, such as which weapons to buy.

According to the GAO, all the spending in the current five-year plan would cost more than $1.5 trillion, but the sources said the actual spending projections are about $100 billion less than that.

The GAO report is part of an ongoing debate between the administration and the Democratic-controlled Congress about the cost of defense spending.

For the past four years, Congress has reduced or frozen the Pentagon budgets and administration critics have charged that the Pentagon is making unrealistic plans for future spending. When those plans are changed, economic problems result, according to the critics.

Unrealistic planning means the Defense Department might be forced to cancel weapons systems after they are started, as evidenced by the current debate over the V-22 Osprey, the Marine Corps plane recently canceled by Defense Secretary Dick Cheney.

The GAO report notes that Bush administration budget planners are assuming that inflation will drop to 1.7 percent by 1994 and calls that projection unrealistic, the sources said.

According to the sources, that unrealistic figure will account for about half the $100 billion.

Most of the rest arises from plans by the Army, Navy, Marines and Air Force to buy weapons that they won't be able to afford in future years because of the current budget crunch, the sources quoted the GAO report as saying.

Bush reduced by about $65 billion the projected defense budgets for fiscal 1990 through fiscal 1994. But according to the GAO, more reductions are needed, the sources said.