Palestinian President Yasser Arafat is not brain dead but his condition is getting worse, his doctor said on Thursday. ‘‘President Arafat does not have cardiac arrest or heart failure,’’ Ashraf al-Kurdi, Arafat’s Jordanian doctor said. ‘‘He is still alive. He is not clinically dead. There is no brain death, but his condition is deteriorating. Because there has been no diagnosis, we don’t know what’s wrong with him.’’ A senior Palestinian official said: ‘‘President Arafat is in very serious condition. He is still in a coma. The sense people are getting is that they are increasingly pessimistic.’’ Arafat’s immune system appeared weak as his health, which had at first stabilised after he arrived at the hospital, suddenly deteriorated on Wednesday, aides said. He was transferred to the intensive care unit on Wednesday at around 5 p.m.