An operation on ailing Prime Minister Ariel Sharon was delayed Tuesday after doctors found an infection in his upper respiratory tract, hospital officials said. Sharon, 78, has been comatose since suffering a stroke on Jan. 4. Doctors on Tuesday had planned to reattach a portion of his skull removed immediately after the stroke. It would have been his eighth surgery since falling ill. Hadassah Hospital spokesman Ron Krumer said the surgery would be postponed until the infection, common in patients in Sharon's condition, is gone. The infection, discovered in a routine exam early Tuesday, is being treated with antibiotics, he added. "There are no rules to how long it could take to go away. It could take one day, it could take two days, it could take two weeks," Krumer told The Associated Press. Krumer said the planned operation is routine for people in Sharon's condition, noting that "every opening in the body is a source for infection." "It's his. We have to give it back at some point. We have to reattach the skull," Krumer said. He declined to say why doctors decided now was the time to reattach the skull. "There are risks. There is no surgery without risks. The minute that you treat a person, and especially in his head, there are risks," Krumer said. Sharon has been treated at Hadassah since the stroke. Israel's Army Radio reported that the reattachment of the skull was the last step before Sharon is moved to a long-term care facility. Krumer refused to confirm the report, but experts in long-term care have examined Sharon in recent weeks. Dr. Haim Ring, the head of the neurological rehabilitation department at Beit Loewenstein Hospital, said the longer Sharon remains comatose the smaller his chances are of waking up. "The question is what his situation will be if he should wake up," Ring told Israel's Army Radio. The stroke suddenly removed the popular prime minister from Israel's political landscape, shortly after he formed the centrist Kadima Party. The stroke shocked Israelis, many of whom believed the ex-general would bring them a more secure future. Kadima won last week's election, although by a smaller margin than was expected when Sharon headed the movement. Analysts have said the party's popularity was a result of Sharon's legacy.