The air portion of the war against Iraq is probably costing "under half a billion dollars a day," Federal Reserve Chairman Alan Greenspan said yesterday, adding that the current actual cost to the U.S. government is far less than that.

Greenspan's testimony before the House Budget Committee offered one of the first assessments of the cost of the Persian Gulf War from a top government official, although the Fed chairman said the calculations were his own and not an administration assessment.

Greenspan indicated that the short-run cost of the war, both in the air and on the ground, will have little direct impact on the U.S. economy. Indirectly, on the other hand, it could have a significant impact, depending on how it affects consumer and business attitudes and the price of oil, he said.

The Fed chairman stressed, however, that it is too soon to consider any sort of tax increase to cover war costs, a possibility clearly on the mind of the committee chairman, Rep. Leon Panetta (D-Calif.) and some other members.

"I think a surcharge at this stage is very clearly premature and, hopefully, unnecessary even under any scenarios which we can contemplate," the Fed chairman declared. "I should hope at this stage that very little in the way of significant fiscal action, other than the {budget} agreement that was pounded together last year, will be required."

In a separate interview, Budget Director Richard Darman also argued that the cost of the war was under control, although he noted the high cost of some of the ordnance being used; for instance, a Tomahawk missile costs $1.3 million, and 100 or more were being fired daily in the first days of the war.

"Presumably, it goes at this level of intensity for at most two or three weeks," Darman said. "Maybe it goes four weeks. It doesn't go for a year; it doesn't go for 10 years. ... So that hunk of expense can be calculated, planned for and handled."

At a news conference after Greenspan's testimony, Panetta gave his backing to a bill introduced by Rep. Charles Schumer (D-N.Y.) that would require that the Office of Management and Budget provide Congress with monthly updates on the war's cost. The figures could be used both as a basis for asking allies, such as Germany and Japan, to contribute a specific share of the cost and in determining whether Congress should try to find some way to pay for them rather than let the budget deficit increase, Panetta said.

Greenspan, who as a private consultant once made detailed cost estimates for both the Korean and Vietnam wars, did his own calculations this time. He said he used only publicly available information, including items such as the number of air sorties being flown each day by U.S. planes, the share that drops bombs or fires missiles at targets -- as opposed to those flying reconnaissance or fighter cover missions -- and the cost of the ordnance used. The cost of the bombs and missiles represents about 75 percent or 80 percent of the total cost, he said.

Because all the ordnance being used is coming out of military stockpiles rather than off current production lines, Greenspan continued, the current budget cost is much less than even half a billion a day.

"If the cost is substantially inventory reduction which would otherwise have been scrapped, then the ... net cost or outlay is negligible," he said. Until there is an assessment of how much war material will be replaced, "I'm not sure we know what the federal ... budget cost is and, therefore, what the effect on federal borrowing is and hence the effect on the economy," he said.

Later he added: "The actual net borrowing cost -- the ultimate measure of this war, if you want to put it in economic and financial terms -- may be a lot lower than we realize. Until we know its order of magnitude, how that is financed strikes me as something which we should not immediately endeavor to assess."

Greenspan contrasted the current situation with that of the Vietnam War, when Defense Department officials found they did not have enough munitions on hand to fight effectively when the conflict began.

That meant orders had to be placed immediately for more arms, which gave a boost to an economy that already was operating at full employment levels.

In contrast, the sort of inflationary pressures that were present in the late 1960s are not evident now, the Fed chairman said.

Instead of being overheated, the economy is declining and is likely to continue to do so until about the middle of the year, he said.

Schumer suggested that other nations should pay at least half of the cost, much more than present pledges of support. "Given the economic strength of our allies and the enormous benefits they derive from the United States presence in the gulf, this small contribution is unacceptable," he said.

Panetta pegged the war's cost at between $500 million and $750 million a day. "I think it would be in our interest not to simply add that to the deficit, but to try to cover those costs in the same kind of pay-as-you-go requirement that we provide for other initiatives in the budget agreement," he said. "Make no mistake about it, I think there is going to be a debate on how we pay for it if the costs are high and our allies have not contributed very much at that point in time. ..."

If the war's cost rises too much, it could undermine last fall's budget agreement, the Budget Committee chairman warned. "I'd like to stay the course. But if these costs grow substantially and the war is a prolonged war, then obviously all bets are off," he said.

House Speaker Thomas S. Foley (D-Wash.) said that while "there are no plans" for any tax increase, "I won't lay that totally aside."

On a related matter, Robert Reischauer, director of the Congressional Budget Office, is expected to tell Congress today that CBO's latest economic forecast includes at least two consecutive quarters in which the gross national product declines after adjustment for inflation. Darman has sent Reischauer a letter authorizing him to say that the administration agrees with that forecast.

Under the terms of last year's budget law, a CBO forecast that the economy will decline two quarters in a row means that the Senate must vote within a few days on whether to suspend the enforcement provisions of the law that limit spending or require that revenue increases must offset new spending for certain benefit programs such as Social Security.

Greenspan, Panetta and the committee's ranking minority member, Rep. Willis D. Gradison (R-Ohio), all said yesterday that they opposed dropping those enforcement provisions despite the recession.