President Bush will undergo a routine colonoscopy Saturday and temporarily hand presidential powers over to Vice President Dick Cheney, White House press secretary Tony Snow said.

Snow told reporters Friday that Bush will have the procedure done at his Camp David, Md., mountaintop retreat.

The last time Bush had colon and rectal cancer surveillance was on June 29, 2002. Doctors then advised him to have another colonoscopy in five years.

"The president has had no symptoms," Snow said.

The procedure will be supervised by the president's doctor, Richard Tubb, and will be performed by a medical team from the National Naval Medical Center at Bethesda, Md.

Snow said that because president will be under the effects of anesthesia, he once again has elected to implement Section 3 of the 25th Amendment to the Constitution. Cheney will serve as acting president until Bush notifies authorities that he is ready to reassume his powers.

In 2002, Bush transferred presidential powers to Cheney for more than two hours during the routine colon screening that ended in a clean bill of health.

It was only the second time in history that the Constitution's presidential disability clause was invoked. President Reagan was the first to invoke the Constitution's 25th Amendment since its adoption in 1967 as a means of dealing with presidential disability and succession.

The earlier colonoscopy for Bush also was done at the well-equipped medical facility at Camp David near Thurmont, Md. Bush felt well enough afterward to play with his dogs and take a 4 1/2-mile walk with the first lady and then-White House Chief of Staff Andrew Card and his wife. He then went to the gym for a light workout.

Tubb said two polyps were discovered during examinations in 1998 and 1999 while Bush was governor of Texas. That made Bush a prime candidate for regular examinations.

The 2002 procedure began at 7:09 a.m and ended at 7:29 a.m. Bush woke up two minutes later but did not resume his presidential office until 9:24 a.m., after Tubb conducted an overall examination. Tubb said he recommended the additional time to make sure the sedative had no aftereffects.