Iraq's war machine, built on the nation's wealth of oil, is running out of gas.

Over the past 2 1/2 weeks, U.S. and British military officials say, allied air strikes have knocked out virtually all of Iraq's oil refining capacity. And analysts calculate that any fuel still in Iraqi and Kuwaiti refineries cannot meet the needs of the Iraqi military.As a result of the damage and a six-month international trade embargo that has cut off all imports, Iraq must draw upon fuel stockpiled before the war started.

The prewar inventories were thought to be considerable. But the regime of Iraqi President Saddam Hussein now is stretching its fuel supplies by halting all sales to civilians and restricting movement of its ground and air forces.

Since Saddam's storage tanks can no longer be refilled, analysts say, it's only a matter of time before Iraq's diminishing fuel supplies are consumed by trucks delivering supplies and other wartime needs. Each battle, the analysts add, will only hasten the day they run dry.

Indeed, the stockpiled oil might not do Iraq much good, analysts say, because Iraq has never had a pipeline network to transport refined oil products and has to truck fuel to the military. With bridges and roads bombed out, moving anything by truck is increasingly difficult.

Military and oil analysts say Iraq's refineries are its Achilles heel. Unlike missile launchers or aircraft, these sprawling complexes of exposed pipes and multistory tanks cannot be moved or sheltered. Also, because of the extreme volatility of the fuel, refineries can be blown up by as little as a spark.

Bombers need not level a refinery to disable it; a refinery can be made inoperable by simply destroying certain critical components. For example, analysts say allied bombers put Iraq's 70,000 barrel-a-day refinery in Basra out of commission by destroying its storage-tank control system.

In addition, analysts say, damage can be easily assessed: A refinery cannot operate without constantly burning a flare, a precaution needed to burn off gases that would build up and possibly explode if part of the refining process shut down unexpectedly.

If the allied forces "see a refinery is operating," said Anthony Cordesman, a military consultant and aide to Sen. John McCain, R-Ariz., "they will just go back in and inactivate them."

Even if only 80 percent of Iraq's refineries were destroyed, analysts say, Iraq would be unable to support its military without dipping into its stored fuel. With 20 percent of its refineries operating, Iraq could produce no more than 80,000 barrels of refined products a day, analysts estimate.

Military analyst Cordesman estimates that even if Iraq's 38-division army were completely stationary, it would consume at least 90,000 barrels of fuel a day. And if all its divisions were engaged, as some have been recently along the Saudi-Kuwaiti border, he figures the Iraqi military's daily fuel needs would be more than 450,000 barrels.

Iraq's refineries typically stockpile 20 days' worth of refined products, analysts say. Since civilian fuel sales have been stopped and military movements limited, analysts think these supplies, if available, might be stretched for 40 days or longer.