"Not only are taxpayers being fleeced by paying that much for oil, but the effect of taking valuable oil, like sweet crude oil, off the market has a disproportionate effect on oil prices," Dorgan has argued. Energy Department officials have countered that the amount of oil being put into the reserve is too small to affect the oil markets, which globally consume 86 million barrels of oil a day.

The department isn't buying the oil directly. It takes oil in lieu of royalty payments on oil pumped from public lands. That oil is then traded for the type of crude needed for the reserve and delivered by the contracting company. The reserve is on the Gulf Coast.

The department also has left open the possibility of spending $584 million later this year to repurchase oil sold from the reserve in 2005 because of supply disruptions caused by Hurricane Katrina.

Two years ago, President Bush temporarily halted the delivery of oil into the reserve as part of a plan "to confront high gasoline prices" as the summer driving season was about the begin.

"When supplies are tight, every little bit counts," the White House said at the time. No shipments to the reserve were made from May 2006 to April 2007.

Weekly average gasoline prices during that period generally remained under $3 a gallon, dipping to $2.16 a gallon at one point, according to Energy Information Administration figures.

On Friday, light sweet crude oil was as high as $106 a barrel and retail gasoline prices surged to a new record of $3.30 a gallon.