It undermines the establishment of an Islamic state:

Osama bin Laden warned Iraq’s Sunni Arabs against joining tribal councils fighting al-Qaida or participating in any unity government, in a new Internet audiotape on Saturday.
“The most evil of the traitors are those who trade away their religion for the sake of their mortal life,” bin Laden said in the tape.
He denounced Abdul-Sattar Abu Risha, the leader of the Anbar Awakening Council, a tribal force fighting al-Qaida in western Iraq, who was killed.