Is now the time for the United States to dip into its Strategic Petroleum Reserve (SPR)?

Leading Senate Democrats say yes, let's bring down rising oil prices. President Bush says no, let's keep adding to the reserve and save it for a possible disruption in supplies. And Sen. John F. Kerry, the presumptive Democratic nominee, says no, don't dip into the reserve, but stop adding to it for a while to boost available supplies and take upward pressure off oil prices.

The reserve is a tempting weapon -- especially in an election year -- to use against high gasoline prices, which Friday reached a record nationwide average of $2.023 a gallon for regular. As of May 21, it held 659.4 million barrels, equal to 54 days of U.S. oil imports or about 100 days of Saudi Arabia's total oil exports. The reserve has a capacity to store 700 million barrels in massive salt caverns in Louisiana and Texas, and it is 94 percent full. The federal government is building it up at the rate of about 100,000 barrels a day. Releasing just a portion of the reserve could nudge oil prices down slightly, though the potential impact is hard to quantify.

It's up to the president to decide how to manage the reserve. "We will not play politics with the Strategic Petroleum Reserve," Bush said after a Cabinet meeting last Wednesday. "That petroleum reserve is in place in case of major disruptions of energy supplies to the United States."

But the difference between a supply "disruption" and a spike in oil prices is partly semantic. After all, how would a supply disruption make its effect known here? By pushing up oil prices, skewing investment priorities and draining dollars out of the United States to oil-exporting nations. Even without a supply disruption, a panic-driven or cartel-driven rise in prices could have dire economic effects.

Some Democrats, consumers, refiners and economists believe the president could choose to respond to prices -- especially if the market were swayed by political worries rather than fundamental supply and demand. That describes, to some extent, the current situation. Daniel Yergin, author of a Pulitzer Prize-winning book on oil and chairman of Cambridge Energy Research Associates, estimates that anxiety and geopolitical risk have contributed $6 to $8 to the current $40 price of a barrel of oil.

Imagine that the Strategic Petroleum Reserve functioned more like the Federal Reserve, seeking to smooth out bumps in the markets without trying to alter the long-term trend. It could have a board of governors to manage the reserve and make it less political but more effective in preventing panics. Strategies could include suspending new deliveries to the reserve or simply delaying them. Though they would have a minor impact on oil supplies, such flexing of the government's muscle could alter market psychology.

That isn't the way the reserve was conceived. President Gerald Ford signed the Energy Policy and Conservation Act in 1975 to establish an oil reserve of up to 1 billion barrels. The act did not set a "trigger" for tapping reserves. It left it to the president to determine whether a drawdown would be required by "a severe energy supply interruption" or by U.S. obligations as a member of the International Energy Agency (IEA).

The legislation defines a "severe energy supply interruption" as one which 1) "is, or is likely to be, of significant scope and duration, and of an emergency nature;" 2) "may cause major adverse impact on national safety or the national economy" (including a spike in oil prices); and 3) "results, or is likely to result, from an interruption in the supply of imported petroleum products, or from sabotage or an act of God."

The first President Bush is the only president to have dipped into the reserve during an emergency. In late 1990, after Saddam Hussein invaded Kuwait, Bush authorized small sales of 5 million (a "test") and 4 million barrels. Prices dropped, then continued to rise along with political tensions. On Jan. 16, 1991, the day the Persian Gulf War began, he authorized the sale of up to 33.75 million barrels more. The sales, combined with victories in the war, pushed oil prices down. In the end, the government sold only about half that much.

In September 2000, President Clinton ordered the release of 30 million barrels from the reserve to dampen prices, despite the misgivings of his Treasury secretary, Lawrence Summers. Companies agreed to "exchange" those barrels for oil they would return the following year. Prices fell from about $37 to about $32 a barrel. Kerry campaign aide Jason Furman says, "The SPR benefits consumers today because it reduces speculative hoarding and the risk premium. Just knowing the SPR is there in the event of a major supply disruption can reduce volatility -- and prices -- for consumers."

The younger Bush has not drawn from the reserve. When unrest in Venezuela halted exports in late 2002, the administration chose not to use emergency stocks. Senior officials, worried that the looming war with Iraq would cause much bigger supply chaos, wanted to save the reserve. The Venezuela disruption was muted by drawdowns of private industry inventories, but oil analysts say that low inventories have contributed to recent oil price increases.

There are many reasons not to dip into emergency reserves to drive down prices. IEA head Claude Mandil said in an interview with the Wall Street Journal last week that doing so would lead to a futile battle with speculators.

Moreover, using reserves to smooth prices lets the Organization of Petroleum Exporting Countries (OPEC) off the hook; now OPEC has responsibility for balancing the market at a reasonable price. This weekend, consumer and producer nations meet in Amsterdam to discuss the situation. Ideally, more production from exporters, not emergency inventories from consumer nations, will calm the markets. Finally, if the market's fears are well grounded, do you want to minimize them?

Some environmentalists argue that a degree of uncertainty about oil prices is good. It could prod Americans to invest in more energy-efficient, environmentally friendly equipment and cars. The amount of energy used for every dollar of economic output today is barely half as much as was used before the 1973-74 oil embargo.

What would a President Kerry do? Furman said, "A Kerry administration will work with consumers, producers, and public policy makers to establish a strategic oil reserve policy that helps consumers while ensuring our nation's energy security." That should keep consumers and oil traders guessing.

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Steven Mufson is deputy editor of Outlook.

Self serve: A station in Menlo Park, Calif., offers its view of rising gas prices. California prices are about 30 cents higher than the national average.