NEW YORK - Former President Clinton set out on a tour of tsunami-ravaged countries last month knowing he needed more surgery on his chest. But his doctors had given him the go-ahead, assuring him that this operation - to fix a lung problem caused by his heart bypass - could wait.

Clinton returns to the hospital Thursday, almost six months exactly after having heart bypass surgery, to have a buildup of fluid and scar tissue removed from his chest. The condition was discovered during a recent X-ray.

The operation, known as a decortication, is described by his doctors at New York-Presbyterian Hospital/Columbia University Medical Center as low-risk.

They will remove scar tissue that is pressing down on his left lung either through a small incision or with a video-assisted thorascope inserted between his ribs.

In an interview with Associated Press Television News, Clinton said he knew he would be having surgery to repair the condition before he left with former President George H.W. Bush on the tsunami visit. He scheduled the operation for later because doctors told him he would not be able to fly after the surgery.

Clinton, 58, passed a full physical before going to Asia and scored in the 95th percentile for his age in a stress test, said Dr. Allan Schwartz, chief of cardiology at New York-Presbyterian.

Tuesday, Clinton went to the Oval Office with the elder Bush to brief President Bush on their tour of Asian countries that suffered heavy losses.

He was planning to play with Bush in a golf tournament for tsunami relief today.

"I feel fine. I just had a little fluid buildup after my surgery," Clinton told APTN. "It's no big deal."

Clinton's wife, Sen. Hillary Rodham Clinton, D-N.Y., said she would be in New York for the surgery and was "very confident about the outcome."

Clinton's problem is a rare complication of his surgery, where inflammation of the lining of the heart develops and fluid builds around it or in the lungs, said Dr. Craig Smith, who performed the bypass surgery in September. He said it occurs in a fraction of 1 percent of cases.

Clinton had been active since his Sept. 6 heart surgery, presiding over the opening of his presidential library in Little Rock, Ark., before joining Bush for the public relations campaign to help raise private funds for the victims of the Asian tsunami.

Clinton underwent quadruple coronary artery bypass surgery Sept. 6 after suffering chest pains and shortness of breath.