A powerful group of Sunni Muslim clerics called Tuesday for a boycott of national elections set for late January to protest the U.S.-led attack against the Sunni insurgent stronghold Fallujah (search).

The group's director, Harith al-Dhari, said the election was being held "over the corpses of those killed in Fallujah and the blood of the wounded."

In the past weeks, al-Dhari's Association of Muslim Scholars (search) has been warning it would call such a boycott if a Fallujah offensive took place.

U.S. and Iraqi government forces launched a full-scale assault Monday night and punched their way Tuesday into the center of the city.

The association is influential among Iraq's Sunni Muslim (search) minority, and U.S. and Iraqi officials have expressed concern that a lack of Sunni participation would raise question about the legitimacy of the vote.