CAIRO, Egypt — Osama bin Laden called for Iraqi insurgents to unite and avoid divisive "extremism," speaking in an audiotape aired Monday and apparently intended to win over Sunnis opposed to al-Qaida's branch in Iraq.

The tape broadcast on Al-Jazeera television appeared to be in response to moves by some Sunni Arab tribes in Iraq that have joined U.S. troops in fighting al-Qaida members, as well as other Sunni insurgent groups that — while still attacking Americans — have formed coalitions opposed to al-Qaida.

"Some of you have been lax in one duty, which is to unite your ranks," bin Laden said in the audiotape. "Beware of division ... Muslims are waiting for you to gather under a single banner to champion righteousness. Be keen to oblige with this duty."