The threat of a worldwide crude oil shortage has receded, but consumers and businesses in the United States and Asia appear to be facing another painful side effect of the Persian Gulf crisis: shortages of gasoline and other fuels because of a lack of refineries to turn the oil into usable products.

Kuwait's huge, sophisticated refineries provided gasoline and diesel fuel for the U.S. military in the Pacific and for commercial users throughout Asia. With those refineries out of business and Saudi Arabia diverting fuel from commercial markets to the immense military buildup there, many oil industry experts believe fuel shortages are likely even if supplies of crude oil are adequate.

The United States is especially vulnerable because more than 100 refineries have closed in this country for economic and environmental reasons in the past decade, while no new ones have been built. The refineries that remain are operating very close -- dangerously close, some experts believe -- to full capacity.

Fear of such shortages is the reason prices of gasoline and jet fuel keep rising, analysts said. While crude oil prices are not as volatile as they were in the initial days of the crisis, they continue to fluctuate. Yesterday, crude oil contracts in New York were up $1.80 a barrel over Friday, closing at $29.12.

Most world attention since Iraq invaded Kuwait has focused on the availability of crude oil. But industry officials say the refining capacity problem preceded the current crisis and has its roots in the economics of the oil industry over the past 10 years -- a period in which more than 100 U.S. refineries have shut down, reducing the nation's refinery capacity to 15.5 million barrels a day from 18 million in 1981. Total world refining capacity, outside the Soviet Union and China, is 55.4 million barrels a day, according to the American Petroleum Institute.

Refiners here and overseas are scrambling to increase their output.

The Ashland Oil Co. refinery in Canton, Ohio, for example, was scheduled to shut down in mid-October for routine maintenance, putting its 66,000 barrels a day of capacity out of commission for four weeks. But now the Ashland, Ky., company is considering a plan to perform only essential repairs and return the refinery to service in a much shorter time, perhaps 10 days.

Houston-based Coastal Corp., meanwhile, is accelerating the reopening of a 50-year-old refinery on the Caribbean island of Aruba that it bought last year. And Saudi Arabia has increased the output of its refinery at Ras Tanura, on the Persian Gulf, by nearly one-third, even though the former operating level was more efficient.

Some tightness in the market has already developed. The Department of Defense has reported difficulty in obtaining enough jet fuel to support the airlift of troops and equipment to Saudi Arabia. Some U.S. airlines are reportedly stockpiling jet fuel. Analysts say that jet fuel and diesel oil are in short supply throughout Asia, which was heavily dependent on supplies from Kuwait.

"We're starting from a tight situation," said the chief executive of one major oil company. "I'm not saying it's the end of the world or anything, but it's going to stay tight."

"OPEC production does not solve the refinery problem," said Theodore Eck, chief economist for Amoco Corp., referring to last week's agreement by the Organization of Petroleum Exporting Countries to allow its members to increase oil production to make up for the loss of Iraqi and Kuwaiti output. "The bottleneck could well be the refinery problem."

U.S. refineries were running almost at full bore even before Iraq invaded Kuwait, and have continued to do so. In the week that ended Aug. 24, capacity utilization at American refineries was 96 percent -- the highest figure industry officials can remember, and a level some experts consider dangerous.

"Whenever the utilization is above 85 percent, the situation becomes literally explosive," according to Peter Beutel, an oil expert at Merrill Lynch & Co.

The embargo on imports from Iraq and Kuwait applies to refined petroleum products as well as crude oil, removing about 1.5 percent of the world's refining capacity, according to one estimate. Other oil-producing countries are making up for most of the lost crude, but it is more difficult to replace the missing refining capacity.

The world has become more dependent in recent years on refining capacity in the Middle East that now is endangered by the crisis there. The United States, which not long ago refined all its own oil, now imports about 11 percent of its refined petroleum products, mostly from Europe and the Caribbean, but also from the Middle East.

"I believe that the most immediate concern here is for {petroleum} products," said Ernie W. Stamper, vice president for administration at Ashland's refining division. "Crude oil is a secondary concern. The crude oil shortage is out there, but it looms in the more distant future."

Many oil industry officials and analysts believe that the tight refining situation could easily result in spot shortages of products -- especially if there is a significant refinery fire or accident in the United States, of which there have been several already this year.

"If people are worried about any one thing that I see in the industry, they're worried about product supplies," Eck said. "By the time the first snow falls, that could be a pretty big problem."

"Refineries are running flat out. If we were to have a major disruption -- heaven forbid, a fire or a major disruption at a plant -- it would produce some problems," said Scott Lovejoy, executive director of the American Independent Refiners Association, a trade group. "Any protracted disruption would be very serious."

"Are you worried about a tight gasoline market? You ought to be," said William Randol, an oil industry analyst at First Boston Corp. in New York. "Depending on how long this thing goes on, we could see gasoline supplies be very tight." For that reason, many Wall Street analysts are recommending that their clients buy stocks in oil refining companies, such as Ashland, because their profits will rise as demand drives up prices.

Not everybody is so pessimistic about fuel supplies. "I wouldn't characterize it as an alarm," said Will Price, president of Chevron USA, the refining and marketing arm of San Francisco-based Chevron Corp., the nation's largest refiner. "In our forecasting, we do not visualize any ratcheting up of prices due to refining capacity."

"The refinery utilization rates are high, but they're in the low 90s {percent}, and they're probably sustainable," said Ron Jones, director of refining for the American Petroleum Institute, a Washington-based industry association.

Other experts argue that higher petroleum prices will reduce demand enough to keep it within the capacity of the world's refining system. If that happens, the burden will fall more heavily on developing countries, which cannot afford to compete with the United States, Japan and Europe for available supplies.

U.S. capacity, meanwhile, is likely to fall further in the next few years, experts say, because of tighter regulations on gasoline quality and refinery pollution. Not a single full-scale refinery has been built in the United States in nearly two decades, and industrial officials and analysts say environmental and economic constraints will continue the drought for the foreseeable future.

Overseas refinery construction, on the other hand, has been robust in recent years because of looser environmental regulations and the desire by oil-producing companies to cut out the middle man and refine their own oil. The effect of that was to increase U.S. dependence not only on imported crude oil but on imported gasoline, jet fuel and heating oil as well.

Analysts at Kidder, Peabody & Co. have calculated the worldwide net loss of refinery output since the Aug. 2 invasion at 855,000 barrels a day: 800,000 in Kuwait and Iraq shut down because of the embargo, 200,000 in Saudi Arabia diverted from commercial markets to military use, and 370,000 in reduced output elsewhere from using lower-quality replacement crude oils, partially offset by a 515,000 barrel increase in output at operating refineries.

That is a shortfall of only 1.5 percent. But analysts say that what matters is not the total but the availability of the "last barrel" needed by a consumer. If the U.S. Air Force and a commercial airline in Southeast Asia are both shopping for jet fuel, for instance, they are going to bid up the price and probably buy more than they need for immediate use. Crude oil output can be increased with relative ease, but refinery expansion requires time and money.

Another problem is that much of the crude oil that OPEC members have promised to produce to make up the loss of Iraqi and Kuwaiti crude is of poorer quality than the oil that was removed from the market. As a result, it takes more oil -- and more expensive processing -- for a refinery to make gasoline and other fuels.

For this reason, some experts say, some of the additional OPEC production is having trouble finding buyers, despite the shortfall in world oil supplies. Venezuela, for example, produces heavy, high-sulfur crude -- closer in composition to asphalt than gasoline -- that most refineries in this hemisphere cannot break down into light fuels such as gasoline and jet fuel. The products most easily made from such heavy crude are industrial fuel oils, for which there is less demand.

While refineries in the United States and Asia are running at near-maximum capacity, there is surplus capacity in some other parts of the world, notably Europe and the Caribbean. But experts say the extra refining capacity is limited and, in any case, those plants don't make the kinds of products -- principally high-quality unleaded gasoline -- needed by the United States. Arnold Safer, a former Exxon Corp. executive who now is president of the Energy Futures Group in Bethesda, estimates that it would cost $8.6 billion and take 20 years to upgrade Caribbean refineries to U.S. standards.

"There is idle refining capacity not in this country but in other parts of the world, but that idle refining capacity is not designed to supply the needs for products that we have," Lovejoy said.