U.S. Embassy officials refuse to negotiate with insurgents or mediate between militants and the Iraqi government, despite overtures by Sunni Arabs claiming to represent armed groups, a U.S. official said Friday. "We do not talk to people who have killed or who provided material assistance," said the official, who spoke to reporters on condition of anonymity because of U.S. government rules. The official said the embassy is often approached by Sunni Arabs who claim to have been sent by insurgents to present demands."We have never negotiated through these people with insurgents. We deliver a very simple message: 'Stop the violence. If you don't stop the violence, eventually our forces will take you out,'" the official said. He said those who approach the embassy are usually academics, businessmen or midlevel officials of the former ruling Baath Party.