Some Iraqi experts question whether a Sunni boycott would be universal. Nazim al-Jassour, a political scientist from Baghdad University, noted that some Shiite-led political parties, like Allawi's Iraq National Accord, have many secular Sunni members.

Al-Jassour, however, said the association has both the means and the support to raise doubts about the credibility of the election.

As expected, Iraq's Shiites — about 60 percent of the population — are embracing the election, encouraged by their clerics who see the ballot as an opportunity for power. A senior aide to Grand Ayatollah Ali al-Sistani — Iraq's top Shiite cleric — told worshippers in Karbala on Friday that failure to vote would be "sinful."

An effective boycott also would deepen the Sunni-Shiite divide, fueling the insurgency and straining the country's fragile ethnic and racial fabric.

The boycott threat comes at a time when the association and Allawi's government are at odds over several issues, including detention of some of its members. The latest arrest occurred Friday, when American troops raided the Baghdad home of senior member Sheik Abdul-Sattar Abdul-Jabbar, taking him and two of his sons into custody.

Al-Kobeisi said 72 association officials are in U.S. or Iraqi government custody.

Deputy Prime Minister Barham Saleh, a Kurd, defended the arrests, telling reporters that those who incite violence "will be punished, whoever he might be."

The association also has opposed Allawi's threats to use force against Fallujah if community leaders do not hand over Jordanian-born terror leader Abu Musab al-Zarqawi and allow government troops to take control of the city.

The association and representatives from the city insist al-Zarqawi, who has carried out numerous car bombings and beheadings of foreign hostages, isn't in the city.

The association has been vehemently anti-American since it was organized shortly after Saddam's ouster last year. On occasion, it has displayed solidarity with Muqtada al-Sadr, a radical Shiite cleric whose supporters fought American forces in two revolts so far this year.

Diaa Rashwan, an Egyptian expert on militant Islamic groups, believes the association has an agenda similar to the national liberation movements of the 1950s and 1960s in the Middle East, Africa and Asia.

"Their only message seems to be the expulsion of foreign troops," he said from Cairo.

Some Iraqis, however, believe the association is functioning like the political wing of a guerrilla army.