A major Sunni political party has quit the interim Iraqi government and revoked its single minister from the Cabinet in protest over the U.S. assault on the insurgent stronghold of Fallujah (search), the party's leader said Tuesday.

The Iraqi Islamic Party (search) wields significant influence over the country's Sunni community and its withdrawal from the government will likely be a blow to Interim Prime Minister Ayad Allawi (search).

"We are protesting the attack on Fallujah and the injustice that is inflicted on the innocent people of the city," said Mohsen Abdel-Hamid, head of the Iraqi Islamic Party.

Abdel-Hamid told The Associated Press the party leaders convened Monday and decided that their one minister in the Cabinet — Minister of Industry, Hajim Al-Hassani — should quit.

"We cannot be part of this attack," he said.

On Monday, Allawi confirmed he had given the greenlight to multinational and Iraqi forces to retake the insurgent-held city of Fallujah, which has become a symbol of Muslim resistance to the U.S. led-forces in Iraq.

U.S. and Iraqi forces pushed into the northern sector of Fallujah after an all-out offensive was launched early Monday to seize the key insurgent strongholds in the city west of Baghdad.

Fallujah has become the major sanctuary for Islamic extremists bent on destabilizing the U.S-backed interim authorities in Iraq.

The Iraqi Islamic Party is the Iraqi branch of the Muslim Brotherhood, a moderate Sunni Islamic party well established in the Middle East.

A prolific author on the Koran, Abdel-Hamid was detained under the regime of Saddam Hussein. The party was suppressed under the former dictator and many of its members were forced to flee abroad.

The Iraqi Islamic Party returned to public life after U.S.-led coalition forces toppled Saddam and established the country's interim authorities.