Al Qaeda's American mouthpiece Saturday urged wannabe terrorists in a new video to act alone instead of trying to join cells attempting 9/11-type spectacular strikes. Californian Adam Gadahn urged individual violent jihad in a 40-minute tape, which endorsed an Al Qaeda ally's call last week for sympathizers to mimic the Ft. Hood killings and attempted bombings over Detroit last Christmas and in Times Square in May. "My brothers: know that Jihad is your duty," Gadahn ranted in Arabic. "You have an opportunity to strike the leaders of unbelief and retaliate against them on their own soil."