American citizens working for al Qaeda overseas can legally be targeted and killed by the CIA under President Bush's rules for the war on terrorism, U.S. officials say. The authority to kill U.S. citizens is granted under a secret finding signed by the president after the Sept. 11, 2001, attacks that directs the CIA to covertly attack al Qaeda anywhere in the world. The authority makes no exception for Americans, so permission to strike them is understood rather than specifically described, officials said. These officials said the authority will be used only when other options are unavailable. Military-like strikes will take place only when law enforcement and internal security efforts by allied foreign countries fail, the officials said.