Pumped by consumer shock at gasoline prices topping $4 a gallon and flowing hard toward $5, political pressure is mounting to end the 1981 moratorium on offshore drilling, which was adopted to protect the environmental and tourism value of the nation's beaches.

President Bush -- who would also open up drilling in the Arctic National Wildlife Refuge and Rocky Mountain oil shale formations in wilderness areas -- says offshore restrictions have become "outdated and counterproductive" in the 27 years since Congress first banned new leases on the outer continental shelf; his father, the 41st president, endorsed that ban in 1990 with an executive order.

Other drilling proponents, including presumptive Republican presidential nominee Sen. John McCain and Florida Gov. Charlie Crist, who reversed his longtime opposition to drilling off his state's gulf coast, say technological advances have significantly reduced the risks of spills from offshore rigs. Mr. McCain pointed to oil platforms in the Gulf of Mexico that weathered Hurricane Katrina as proof offshore drilling is safe.

But even if newer technologies reduce the risk of environmental degradation from offshore drill rigs, energy experts question if the amount of recoverable oil is worth the risk. Environmental groups charge oil companies with opportunistically using recent gas pump increases to try to stockpile federally owned land and offshore drilling acreage before developing all the areas that they already have under lease.

Only 10 million acres of the 44 million acres already leased, mostly in the western Gulf of Mexico, are producing oil or gas, although oil companies say some of the other acreage is in development.

The producers explain that they are not pumping more, in part, because drill ships and drilling rigs are in short supply and that offshore drilling remains extremely expensive. Each well requires an investment of $100 million or more and can take years to develop.

Guy Cantwell, a spokesman for Transocean Inc., the world's largest ocean drilling company, with a fleet of 138 drilling units including nine ultra deep water units, said environmental safety has improved even as drilling is occurring in deeper and deeper water.

Advances in safety

In the years since the moratorium began, drilling technology has advanced, with big "jackup rigs" and mobile "semi submersible" rigs able to provide more stable drilling platforms even in high seas, he said. And "drill ships" using sonar and global positioning satellite data and computer-directed propellers are able to hold their positions and sink wells in water depths up to 12,000 feet. Offshore oil and gas transfer and storage is safer as well.

"We're drilling 100 miles offshore in water depths of 10,000 feet and more. Some of those wells are very challenging but we're able to conduct the drilling safely and efficiently," Mr. Cantwell said.

According to the U.S. Department of the Interior's Minerals Management Service, which tracks operation of the 4,000 oil and gas production facilities and 33,000 miles of pipeline operating on the outer continental shelf, spills and "blowouts" -- which occur when drillers lose control of a drilling operation and oil gushes out of the well and into the sea -- have declined significantly in recent years.

From 1985 through 2001, outer continental shelf wells produced more than 7 billion barrels of oil while spilling only about 68,500 barrels. In that period, well drilling blowouts caused only two spills of more than 5 barrels -- an 11 barrel blowout in 1992 and a 200 barrel blowout in 2000.

But offshore drilling accidents can be devastating. The 10 worst drill rig accidents dating to 1962 killed more than 770 workers. The five worst well "blowouts" -- all occurring between 1969 and 1980 -- spilled more than 4 million barrels of oil.

Two of those blowouts blackened beaches in the United States. In 1969, a blowout at Union Oil's Alpha Well A-21 operating in the channel off Santa Barbara, Calif., lasted 11 days and spilled 80,000 barrels of oil, soiling California beaches.

The biggest oil spill in history -- 14 times bigger than the 11 million gallon Exxon Valdez spill -- occurred in 1979 after a blowout on a drill platform operated by Petroleos Mexicanos in the Gulf of Mexico. More than 3.5 million barrels of oil -- 147 million gallons -- poured into the gulf for nine months and caused extensive damage along the Texas coast.

About 20 percent of the continental shelf is already open for drilling. Last year offshore wells produced more than 492 million barrels of oil -- about 27 percent of all the oil produced in the United States -- and more than 2.8 trillion cubic feet of natural gas or 14 percent of the domestically produced total.

Dr. Lester Lave, a Carnegie Mellon University economics professor with research interests in quantitative risk assessment and climate change among many others, agrees that the United States should open up some of its offshore areas for drilling, but only after it first pursues a comprehensive policy of energy efficiency. That would be the easiest and least expensive way to boost the amount of available oil.

"We can save more oil through energy efficiency and conservation than we can possibly find offshore -- several million barrels a day if our cars averaged 50 miles per gallon," Dr. Lave said.

Conservation could also have more of an effect sooner, rather than waiting the five to 10 years many energy experts say it would take to get new lease areas into production.

"I think we ought to get that oil because we can do it safely and without appreciable environmental damage, but I want to go where the money is first -- that is in energy efficiency and conservation," Dr. Lave said. "Only when we are committed to that path would I go after the offshore oil. And I would bet that the majority of people who oppose offshore drilling would agree with me."

Action in Congress

However U.S. Rep. Jason Altmire, D-McCandless, who joined most Democrats in Congress in rejecting President Bush's call to open up the seas for drilling earlier this month, said oil companies should fully explore their existing leases before additional areas are opened.

"With gas prices above $4," he said, "it is time for oil companies to start producing on the more than 68 million acres of federal land that they hold leases to right now.

The unused areas already under lease could produce an additional 4.8 million barrels of oil and 44 billion cubic feet of natural gas each day, Mr. Altmire said. That amount of oil would nearly double the current domestic oil production, and is more than six times the estimated peak production the Arctic National Wildlife Refuge could provide 20 years from now.

The world consumes about 86 million barrels a day. The U.S. share of that is about 20.6 million barrels, 60 percent of it from foreign sources. Current estimates are that the offshore areas covered by the moratorium contain a total of 19 billion barrels, enough to provide about 920 days, or about 2.5 years, of current U.S. consumption.

U.S. Rep. John Peterson, R-Venango, a longtime supporter of extractive industries and leader of House efforts to open offshore drilling, said there is likely much more oil and gas than we know about offshore, and Congress should lift the moratorium and let the oil companies look for it.

"We've only looked in depths up to 4,000 feet and modern seismographic techniques haven't been used," Mr. Peterson said. "We could have the greatest oil and gas find in the history of the country but we haven't been allowed to look. So for us to starve the country's energy supply as we develop renewables is nonsense. Until we get there we can't shut down oil.

Mr. Peterson said many of the offshore areas where drilling is prohibited are more promising than the areas already leased.

"I've got an angry constituency out there," he said, "and the simplest thing we can do, and the most environmentally sensitive, is to drill offshore."