US President George W. Bush said today he will undergo a routine colon test tomorrow that will require him to be sedated.
He will transfer power briefly to Vice President Dick Cheney.
Mr Bush said he had no signs or symptoms of illness but that the last time he had a colonoscopy five or six years ago some benign polyps were discovered.
"This is a routine physical examination that will be done at Camp David," Mr Bush told reporters as he prepared to leave for his presidential retreat for the weekend.