Rising oil prices, Persian Gulf uncertainties and the reluctance of some banks to lend money combined last month to produce a "meaningful downturn" in the U.S. economy that has continued into November, Federal Reserve Chairman Alan Greenspan declared yesterday.

"What we're looking at is a gradual decline" that will result in negative gross national product in the fourth quarter, if it persists, Greenspan told the House Banking Committee. By "negative," he meant a decline in the GNP, adjusted for inflation, a measure that increased at a revised 1.7 percent annual rate in the third quarter, the Commerce Department reported yesterday.

Greenspan said it is still too soon to tell whether the gradual decline will turn out to be deep enough or last long enough to be labeled a recession. For that reason, and because of concern about inflation pressures, he turned aside suggestions from some congressmen that the central bank lower interest rates substantially to give the economy a boost.

Some members of the committee from East Coast states challenged the idea that a recession has not started. Rep. Charles E. Schumer (D-N.Y.) asked why there is such a discrepancy between what the statistics are showing and what people believe is happening.

"The world out there, when you look at the hard data, is not in as bad a shape as it feels," Greenspan responded. "If the economy were as bad at this point, or was just about to get as bad as a number of my friends and your friends keep telling us, we should see weaker numbers in a number of key areas.

"I will just tell you, as a forecaster from way back, I don't think one dismisses people's views of the way the economy is going as being irrelevant. They are quite relevant. But they have, in the past, been wrong. And I think we have to be prepared for the possibility that it is being overdone.

"I don't want to take a position at this stage because, frankly, I don't know," Greenspan said.

If Iraq had not invaded Kuwait on Aug. 2, the current downturn likely would not have occurred, Greenspan said.

"A significant part of the weakness we're looking at, and conceivably a major part of it, is Persian Gulf-related," he said.

Greenspan turned to figures released yesterday by the Commerce Department to support his argument. If it is a recession, "you should not have the level of passenger car sales and light truck sales that we have currently. There's got to be a mistake in those durable goods order figures that came out this morning," he said.

The Commerce Department said yesterday that new orders for long-lasting items such as autos, airplanes, machine tools and computers rose 3.6 percent last month following two consecutive monthly declines. While the greatest strength was for new aircraft, orders of other goods were stronger than most analysts expected and were not consistent with the onset of a well heralded slump.

On Tuesday, car dealers reported new car sales ran at a 7.1 million unit annual rate in the middle 10 days of this month and averaged a 6.8 million annual rate for the first 20 days. The rates are roughly in line with those of the first half of the year but lower than those of the third quarter.

Despite such figures, most forecasters do believe the economy is in a recession. One of them, Allen Sinai, chief economist of the Boston Co. investment firm in New York, who testified after Greenspan, said a recession probably began even before the Iraqi invasion. The Persian Gulf situation has made the downturn worse and he expects it to continue until the middle of next year, he said.

Aside from the spreading impact of the confrontation with Iraq, Greenspan said the growing unwillingness of some banks to lend to creditworthy customers because of the banks' own troubles is also hurting the economy.

In July the Fed reduced its target for the federal funds rate -- the interest rate banks charge each other for overnight loans -- by a quarter of a percentage point to offset this tightening of terms and other conditions banks were attaching to new loans. "Data since then, including Federal Reserve surveys of bank lending officers, as well as the recent sluggishness of the monetary aggregates, suggest that the tightening of credit has proceeded somewhat further since July," Greenspan said.

"The available anecdotal information clearly suggests that many types of businesses are encountering greater difficulty obtaining financing. This has been seen most clearly in the commercial real estate market, but it extends to borrowing for a variety of other purposes," he said.

Businesses unable to get loans or lines of credit often have to cut back their operations, or in some cases, go out of business, and in either case, economic growth is reduced.

Nevertheless, Greenspan said he would not favor relaxing requirements for the amount of capital financial institutions must have or ask bank examiners to go easy on the way in which they classify problem loans.

Greenspan noted that since the spring of last year, the central bank has cut its target for the federal funds rate to 7.5 percent from nearly 10 percent in response to the weakening economy, the recent agreement to reduce future federal budget deficits and the credit situation.

He made no commitments about what comes next, however.