By Roberta Rampton

WASHINGTON (Reuters) - Strategic reserves of oil should be kept for true supply shocks seven top Republicans in the Senate told President Barack Obama on Monday, urging the White House to avoid tapping stockpiles unless there is a "severe" disruption.

The White House has said for months it was considering the merits of selling oil from the Strategic Petroleum Reserve, or SPR, as a tool for dealing with oil prices spooked higher by Middle East tensions and Western restrictions on Iranian oil sales.

Republican Senate Leader Mitch McConnell and six other senators told Obama in a letter that despite tensions, "we have not yet seen the discrete event that directly affects our oil supply and justifies tapping our reserves.

"The SPR is America's rainy-day fund," the senators said.

"We ask you to preserve it for a truly rainy day with an unanticipated energy or severe supply disruption occurs," said the letter, also signed by Jon Kyl, John Thune, John Cornyn, Roy Blunt, James Inhofe and John Barrasso.

Cornyn said a release would be a "political raid" of the SPR ahead of the November 6 presidential election.

Current reserves are about 695 million barrels stored in salt caverns designed to hold a total of 727 million barrels. The government loaned 1 million barrels last month to refiner Marathon Petroleum Corp due to shortages caused by Hurricane Isaac.

The senators also asked the White House to provide a "detailed plan" explaining how the administration will refill the SPR after selling 30 million barrels last year, when a civil war in Libya cut the country's oil exports.

That move lowered prices only for a few weeks. "Even if your administration flooded the market with the entire remaining SPR stock, it would cause barely a ripple in the price of oil and gasoline," the senators said.

(Additional reporting by Patrick Rucker and Matt Spetalnick in Washington and Joshua Schneyer in New York; Editing by Bob Burgdorfer)