The defense establishment on Thursday rejected Hizbullah leader Sheikh Hassan Nasrallah's announcement a day earlier that Israeli air force navigator Ron Arad, who disappeared after his plane was shot down over Lebanon in 1986, was dead. "Our working assumption is that he is alive," one official said. "Unless someone is brought back to Israel dead and in a coffin, then the assumption is that he is alive." The IDF released a statement saying that their working assumption is that Ron Arad is still alive, unless concrete proof is received to the contrary. "The defense establishment works around the clock to obtain new information regarding Arad's fate in the hope of bringing him home," IDF officials said. On Wednesday night, in the first such comments by the Hizbullah leader, Nasrallah told a Lebanese news station: "My deduction is two words: 'Dead and lost.'" "Regretfully, if we had tangible information we would have achieved an important deal," he said, referring to Israeli demands for news on Arad in return for an additional exchange of Arab prisoners held by Israel. Lawyer for the Arad family Eliad Shraga slammed Nasrallah, claiming that his assumption was baseless. "When it was expedient for him, he said he was alive," Shraga said. "When it was expedient for him, he said he had information on Ron's whereabouts. He is the master of manipulation." Former Shin Bet (Israel Security Agency) chief Avi Dicther backed up Shraga, claiming that the Hizbullah chief's remarks were manipulative. "The official Israeli assumption and mine is that Ron Arad is still alive," Dichter told Army Radio. "Nasrallah is a known manipulator." Dichter further rejected Nasrallah's suggestion that Arad could have died in the Lebanese countryside after escaping his captors in 1989, claiming it contradicted Israeli intelligence.