In a reversal, Barack Obama is proposing tapping the nation’s strategic oil reserves to help drive down gasoline prices, his campaign said Monday.

In the past, Obama has not advocated tapping the oil reserve, but campaign spokeswoman Heather Zichal said he has reconsidered. “He recognizes that Americans are suffering,” she said.

The nation’s strategic petroleum reserve contains 707.2 million barrels in salt caverns in Texas and Louisiana. It was last tapped shortly after Hurricane Katrina. Otherwise, President Bush has refused to use the reserves, saying they need to be left intact as an emergency stockpile. However, in the face of strong congressional pressure, Bush in June stopped filling the reserve until oil prices decline.

Obama’s call for using the government reserve mirrors a proposal that has been pushed by congressional Democrats, but opposed by Republican leaders and the White House.

House Speaker Nancy Pelosi, D-Calif., for weeks has called for Bush to withdraw a “small amount” of oil from the government reserve to add to supplies and try to force down prices.

The Strategic Petroleum Reserve is capable of releasing about 4 million barrels a day. It’s unclear what impact such release might have on global oil prices, or costs of gasoline at the pump.

The new Obama ad trumpets his proposal to revive a windfall profits tax on energy companies and asserts that McCain favors tax breaks for the oil industry.

“A windfall profits tax on big oil to give families a thousand-dollar rebate,” an announcer in the ad says.

Obama has pushed for such a tax to fund $1,000 emergency rebate checks for consumers besieged by high energy costs.

Congress enacted a windfall profits tax in 1980, during an earlier era of high oil prices, but repealed it in 1988 amid concerns the tax was discouraging domestic oil development.

The new ad opens with a driver pumping gas. The announcer says, “Every time you fill your tank, the oil companies fill their pockets.”

Republicans were quick to pounce.

“Barack Obama’s latest attack ads shows his celebrity is matched only by his hypocrisy,” said McCain spokesman Tucker Bounds. “After all it was Senator Obama, not John McCain, who voted for the Bush-Cheney energy bill that was a sweetheart deal for oil companies. Also not mentioned is the $400,000 from big oil contributors that Barack Obama has already pocketed in this election.”

Obama said Friday that he would reluctantly consider accepting some new offshore oil drilling. Obama previously opposed any offshore drilling. He praised a plan unveiled by a group of Republican and Democratic senators to permit limited drilling off Southern states while supporting an effort to convert most vehicles to alternative fuels in 20 years.