Vice President Cheney will undergo elective surgery to treat a blood vessel problem behind his right knee, the White House announced yesterday.

The elective procedure, which will probably take place next weekend at George Washington University Hospital, will treat an aneurysm in an artery that was discovered earlier this year during a routine checkup, spokesman Steve Schmidt said.

"It is a condition that needs to be addressed so as not to become a problem over time," Schmidt said.

The procedure will be performed under local anesthetic and will involve a short hospital stay, Schmidt said.

An aneurysm is a weak spot in an artery that can burst if left untreated. Those in the knee tend to be less likely to burst than those located elsewhere, but they can lead to the formation of blood clots, which can break off and cause a dangerous blockage of blood circulation in the leg.

"If that occurs, you can risk losing a leg," said Jade Hiramoto, a vascular surgeon at the University of California at San Francisco.

Typically, such aneurysms are repaired by taking a piece of a vein from elsewhere in the leg and bypassing the weakened part of the artery, Hiramoto said.

"We create a detour and exclude that segment from circulation," she said. "It's a fairly straightforward procedure. The risk of complications are fairly low."

Cheney, 64, has a history of heart problems, dating to 1978, when he suffered the first of four heart attacks. Over the years, Cheney has undergone a series of treatments, including a quadruple bypass in 1988. In June 2001, doctors inserted a special pacemaker, known as an implantable cardioverter defibrillator, into Cheney's chest to help regulate his heartbeat.

Staff writer Peter Baker contributed to this report.