Bush planned to hand over authority to Cheney on Saturday before the president goes under anesthesia to receive a routine colonoscopy ¡ª a test to look for potential cancer. The same routine was followed when Bush underwent a colonoscopy in 2002.

Saturday's procedure was to be performed at Camp David, the presidential retreat in Maryland's Catoctin Mountains. At the time, Cheney was to be at his home on the Chesapeake Bay in St. Michaels, Md., about 45 miles east of Washington.

Two polyps were discovered during examinations in 1998 and 1999 while Bush was governor of Texas. In 2002, Bush had no symptoms and doctors recommended another test in five years.

"Although no polyps were noted in the exam in 2002, age and history would suggest that there's a reasonable chance that polyps will be noted this time," said White House press secretary Tony Snow. "If so, they'll be removed and evaluated microscopically." Bush is 61.

Snow, himself a cancer sufferer, said results would be available after 48 hours to 72 hours, if not sooner.

Snow had his colon removed in 2005 and underwent six months of chemotherapy after being diagnosed with colon cancer. On March 26, he underwent surgery to remove a growth in his abdominal area, and doctors determined that cancer had metastasized, or spread, to the liver.

Saturday's procedure was to be supervised by Dr. Richard Tubb, the president's doctor, and performed by a team from the National Naval Medical Center at Bethesda, Md.

In transferring power while under anesthesia, Bush is electing to implement Section 3 of the 25th Amendment to the Constitution, making Cheney acting president until Bush indicates he is prepared to reassume his authority. It has been invoked only twice before. The first time was in July 1985 when President Reagan underwent surgery and turned over power to his vice president, Bush's father. The other time was in 2002.