Washington ? President Bush said he will briefly transfer the powers of the presidency to Vice President Dick Cheney today while under sedation for a colon screening.

For only the second time, the 25th Amendment of the Constitution will be invoked and Cheney will be acting president for “a matter of hours,” White House counsel Al Gonzales said after the surprise announcement.

Vice President Dick Cheney addresses delegates at the Southern Republican Leadership Conference in Charlotte, N.C.. President Bush said Friday he would briefly transfer the powers of the presidency to Cheney today, when Bush undergoes a colon check that will require him to be sedated.

Bush, who turns 56 next week, said doctors recommended the procedure a colonoscopy because benign polyps were found in two previous checks. It is considered a standard preventive procedure for men his age.

The president said there were “no signs, no symptoms” of trouble and he expected to exercise in the afternoon after the check. 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.

Little used clause

Gonzales said Section 3 of the 25th Amendment enacted in 1967, four years after President 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 Reagan underwent surgery for colon cancer.

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

Tubb said a sedative called propofol would 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.

Tubb will join a military medical team lead by endoscopist Dr. James Butler, a Navy captain and chief of gastroenterology at the National Naval Medical Center at Bethesda, Md.

The level of sedation including whether Bush is fully unconscious will be decided depending on the president’s comfort level, the doctor said.

‘Because we’re at war’

Bush said the test was routine but the times were not, the reason he will be transferring power.

“I’m the first president to have done so under this type of procedure and/or physical examination. I did so because we’re at war,” Bush said.

Before taking the test, Bush will be given a solution to drink to cleanse his system.

A colonoscopy is considered the best way to examine the colon and to find and remove polyps. The procedure, performed regularly, is thought to reduce the risk of colon cancer by up to 90 percent. More than 2 million are performed annually in the United States.

The procedure uses a flexible tube containing an optical scope that enables the doctor to view the entire length of the colon. A wire cutter can be threaded through the tube and used to remove any polyps discovered.

Generally, physicians recommend that people after the age of 50 receive a colonoscopy every three to five years, depending on the patient’s personal and family history of colon cancer. For some patients, the procedure is done annually.

Bush made the announcement in good spirits, joking with reporters about the procedure and the short time that Cheney will be president.

Cheney will be in Washington this weekend.