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But now, a vocal minority of experts says world oil production is at or near its peak. Existing wells are tiring. New discoveries have disappointed for a decade. And standard assessments of what remains in the biggest reservoirs in the Middle East, they argue, are little more than guesses.

"There isn't a middle argument. It's a finite resource. The only debate should be over when we peak," says Matthew Simmons, a Houston investment banker and author of a new book that questions Saudi Arabia's oil reserves.

Today's gasoline prices are high because Hurricanes Katrina and Rita disrupted oil production in the Gulf of Mexico. But emergency supplies from strategic oil reserves in the United States and abroad can largely compensate for that temporary shortfall. If the "peak oil" advocates are correct, however, today's transient shortages and high prices will soon become a permanent way of life. Just as individual oil fields inevitably reach a point at which it gets harder and more expensive to extract the oil before output declines, global oil production is about to crest, they say. Since 2000, the cost of finding and developing new sources of oil has risen about 15% annually, according to the John S. Herold consulting firm.

As global demand rises, American consumers will find themselves in a bidding war with others around the world for scarce oil supplies. That will send prices of gasoline, heating oil and all petroleum-related products soaring.

"The least-bad scenario is a hard landing, global recession worse than the 1930s," says Kenneth Deffeyes, a Princeton University professor emeritus of geosciences. "The worst-case borrows from the Four Horsemen of the Apocalypse: war, famine, pestilence and death."

He's not kidding: Production of pesticides and fertilizers needed to sustain crop yields rely on large quantities of chemicals derived from petroleum. And Stanford University's Amos Nur says China and the United States could "slide into a military conflict" over oil.

Rising global demand for oil

There's no question that demand is rising. Last year, global oil consumption jumped 3.5%, or 2.8 million barrels a day. The U.S. Energy Information Administration projects demand rising from the current 84 million barrels a day to 103 million barrels by 2015. If China and India � where cars and factories are proliferating madly � start consuming oil at just one-half of current U.S. per-capita levels, global demand would jump 96%, according to Nur.

Such forecasts put the doom in doomsday. Many in the industry reject the notion that global oil production can't keep up. "This is the fifth time we've run out of oil since the 1880s," scoffs Daniel Yergin, who won a Pulitzer Prize for his 1991 oil industry history The Prize.

In June, Yergin's consulting firm, Cambridge Energy Research Associates (CERA) in Cambridge, Mass., concluded oil supplies would exceed demand through 2010. Plenty of new oil is likely to be found in the Middle East and off the coasts of Brazil and Nigeria, Yergin says.

"There's a lot more oil out there still to find," says Peter Jackson, a veteran geologist who co-authored the CERA study.

Based on current technology, peak oil production won't occur before 2020, Yergin says. And even if it does, oil production volumes won't plummet immediately; they'll coast for years on an "undulating plateau," he says.

Debate growing sharper

Both sides in the peak oil controversy agree that oil is a finite resource and that every year, the world consumes more oil than it discovers. But those are about the only things they agree upon.

As the debate has persisted, it's grown personal. "Peak oil" believers disparage those who disagree as mere "economists" in thrall to the magic of the marketplace or simple-minded "optimists" who assume every new well will score.

Yergin emphasizes that the CERA study was developed by geologists and petroleum engineers, not social scientists. Of Simmons, Yergin says: "He's wonderful at stirring up an argument and slinging around rhetoric. ... For some of these people, it seems to be a theological issue. For us, it's an analytic issue."

When they're not trading insults, the two sides disagree fiercely over the likelihood of future technology breakthroughs, prospects for so-called unconventional fuel sources such as oil sands and even the state of Saudi Arabia's reserves.

The world's No. 1 oil exporter, in fact, is at the center of Simmons' new book, Twilight in the Desert: The Coming Saudi Oil Shock and the World Economy, which has reinvigorated the peak oil argument.

Simmons says it's impossible for global production to keep up with surging demand unless the Saudis can increase daily production beyond today's 9.5 million barrels and continue pumping comfortably for decades. And, indeed, Yergin is counting on the Saudis to reach 13 million barrels a day by 2015.

Yet while the oil reserves of U.S. firms are verified by the U.S. Geological Survey, the Saudis � like other OPEC countries � don't allow independent audits of their reservoirs. So when Riyadh says it has 263 billion barrels locked up beneath the desert, the world has to take it at its word.

Simmons didn't. Instead, two years ago, he pulled about 200 technical papers from the files of the Society of Petroleum Engineers and performed his own assessment. His conclusion: The Saudis are increasingly straining to drag oil out of aging fields and could suffer a "production collapse" at any time.

Yergin is more optimistic both about the Saudis and the industry's prospects in general. If the past is any guide, technological breakthroughs will reshape both demand and supply, he says. In the 1970s, for example, the deepest offshore wells were drilled in 600 feet of water. Today, a Chevron well in the Gulf of Mexico draws oil from 10,011 feet below the surface.

Widespread use of technologies such as remote sensing and automation in "digital oil fields" could boost global oil reserves by 125 billion barrels, CERA says. Already, advanced software and "down hole measurement" devices to track what's happening in the well have elevated recovery rates in some North Sea fields to 60% from the industry average of 35%, Jackson says.

Technology also won't stand still on the consumption side of the equation, Yergin says. "By 2025 or 2030, we'll probably be moving around in vehicles quite different from the ones we drive today. Maybe we'll be driving around in vehicles that get 110 miles to the gallon," he says.

That's more than a guess. Toyota's 2001-model Prius hybrid got 48 miles per gallon; the 2005 model was up to 55 mpg. If automakers focused solely on energy efficiency, 110 mpg isn't out of the question.

Still, breakthroughs don't just happen, and in the late 1990s, after oil prices fell as low as $12 a barrel, major oil companies slashed research spending. Some who previously doubted the peak oil claims now wonder whether the industry is equipped to develop the necessary innovations.

"Before 1998, I was on the side that said, 'Technology solves all problems,' " says Roger Anderson of Lamont-Doherty Earth Observatory of Columbia University. "The problem is, after $12 oil, oil companies responded by merging and firing large portions of their technical staff."

Now, the International Energy Agency in Paris estimates that $5 trillion in new spending is needed over the next 30 years to improve exploration and production.

The limits of technology

As oil prices � now about $63 a barrel � stay elevated, so-called unconventional supplies of oil become economically feasible. Exhibit one: enormous deposits of Canadian oil sands, which could eventually yield more than 170 billion barrels of oil. On the list of the world's biggest oil countries, that total puts the USA's northern neighbor behind only Saudi Arabia.

That's the good news. The bad news is that wringing oil from the sludge-like tar sands is difficult and costly, and requires enormous quantities of water and natural gas � itself an ever-pricier fuel.

Deffeyes calls talk of substantial tar sands production "the fantasy of economists," adding: "They believe if you show up at the cashier's window with enough money, God will put more oil in the ground."

In recent months, the peak oil camp has received support from some fairly sober quarters, including the U.S. government. A 91-page study prepared in February for the Energy Department concluded: "The world is fast approaching the inevitable peaking of conventional world oil production ... (a problem) unlike any yet faced by modern industrial society."

So far, almost no one in government is calling for immediate action because of the peak oil argument. But in a recent interview with USA TODAY, Energy Secretary Samuel Bodman sounded less than sanguine about the future.

"There's plenty of oil to deal with this over the near term, five years. But if you look out over the next 20, 25 years, we expect demand to grow 50% to 120 million barrels a day. I wouldn't want to opine that's available," says Bodman, a former professor of chemical engineering at Massachusetts Institute of Technology. "It could be, but I don't know."