If President Bush orders an attack against Iraq, the American force would be half the size of that in the 1991 war. The Pentagon's war plans call for deploying as many as 250,000 military personnel, but the initial offensive should start with a much smaller number, with a sizable force in reserve.

The budget director's projections today served as a more politically palatable corrective to figures put forth by Mr. Lindsey in September, when he said that a war with Iraq might amount to 1 percent to 2 percent of the national gross domestic product, or $100 billion to $200 billion. Mr. Lindsey added that as a one-time cost for one year, the expenditure would be ''nothing.''

Mr. Lindsey was criticized inside and outside the administration for putting forth such a large number, which helped pave the way for his ouster earlier this month. He could not be reached for comment this evening. (Congressional Democrats have estimated that the cost would be $93 billion, not including the cost of peacekeeping and rebuilding efforts after a war.)

But today, Mr. Daniels sought to play down his former colleague's remarks. ''That wasn't a budget estimate,'' he said. ''It was more of a historical benchmark than any analysis of what a conflict today might entail.''

Pentagon officials say the cost of munitions in a potential war with Iraq will not be materially more than the cost of munitions in the 1991 gulf war. The reason, they say, is that the military now uses more precision-guided bombs, which are far more accurate, so fewer are needed.

In 1991, about 10 percent of bombs and munitions were precision guided. In the conflict in Afghanistan, the share of precision weapons rose to about 60 percent.

Although precision-guided bombs cost more than conventional munitions, they are not always exorbitantly more expensive, at least by Pentagon standards. Many of the ''smart'' bombs used in Afghanistan, for example, were simply 2,000-pound unguided bombs with a $20,000 mechanism attached to the bomb's tail that allowed it to be steered to a target by satellite.