Prime Minister Ariel Sharon remained in critical but stable condition on Thursday, more than two weeks after he suffered a massive stroke, Hadassah Hospital spokesman Ron Krumer said. Sharon remains in a coma from the January 4 stroke. The hospital said on Wednesday that Sharon underwent successful surgery to replace his breathing tube because of what was termed a "technical problem." The 77-year-old Israeli leader, who has been on a respirator, underwent a tracheotomy Sunday. He has been taken off anesthetics that kept him in a medically induced coma, but has yet to awaken. Outside experts said his failure to regain consciousness in recent days bodes poorly for his recovery.