The procedure will be conducted at the Camp David presidential retreat.

"I feel great," Bush said before leaving the White House for the weekend. "This is part of the annual physical, so I just decided to do it at this time. It fit in with my schedule."

Bush said he decided to transfer powers to Cheney out of extra caution because the nation is at war. Cheney will be "standing by. He realizes he's not going to be president that long," Bush said.

White House physician Dr. Richard Tubb said Bush underwent the same procedure in July 1998 and December 1999; both times two polyps were found.

The procedure usually takes 30 to 45 minutes, Tubb said.

"This is preventive medicine at its finest," the doctor said. "If you're over 50 you ought to make it part of your practice as well."

The doctor briefed reporters shortly after Bush made his plans public before boarding Marine One for Camp David. Aides said he decided to undergo the procedure two or three weeks ago.

Gonzales said Section 3 of the 25th Amendment--enacted in 1967, four years after President John F. Kennedy's assassination--will be invoked by Bush in a letter faxed to congressional leaders and signed by the president.

A second letter, also signed by Bush, will formally transfer powers back, he said.

The only other time Section 3 was invoked was July 13, 1985, when President Ronald Reagan underwent surgery for colon cancer.

White House spokesman Ari Fleischer said the administration will announce that the powers of the presidency were transferred only after Bush recovers and takes back control.

Tubb said a sedative called Propofol will be administered to Bush through an intravenous line. It takes effect in a minute or less and wears off quickly.

"You can turn the medicine off and the patient wakes right up," he said.

The level of sedation will be decided depending on the president's comfort level, the doctor said.

Cheney will be in Washington this weekend.

AP