In an online rant, US-born Adam Gadahn called on fanatics living in "America, Britain and Israel" to attack "enemies of Islam."
He urged recruits to copy ex-London student Umar Abdulmutallab, accused of trying to blow up a passenger jet.
Gadahn has a million dollars bounty on his head.
"I call on every honest Muslim in America, Britain and Israel to prepare to play his due role in repelling the aggression of the enemies of Islam," The Sun quoted Gadahn, as saying.
"This is a golden, once-in-a-lifetime opportunity to reap the rewards of jihad and martyrdom," he added. (ANI)