US warplanes bombed the eastern edges of the rebel-held city of Falluja today, witnesses said, adding about 10 missiles were fired.
US marines are poised for a full-scale offensive on Falluja, 50 km (32 miles) west of Baghdad, to crush Sunni Muslim insurgents they say are holed up there.
It was not clear if there were any casualties. There was no immediate comment from the US military.
Earlier Brigadier General Denis Hajlik told reporters at a base near Falluja that "We are gearing up for a major operation" .
"If we do so, it will be decisive and we will whack them."
Hajlik, deputy commander of the 1st Marine Expeditionary Force, said the expected assault would involve Iraqi forces.
Iraq's US-backed interim government has vowed to pacify the whole country before nationwide elections due in January.
US planes have launched almost daily air strikes on what the military says are safe houses used by a network of Iraqi and foreign fighters led by Jordanian Abu Musab al-Zarqawi.
The latest air raid today killed three Iraqi men and wounded three more civilians, hospital officials said.
A full-scale US-led offensive could be as devastating as a marine attack in April that Washington called off after a world outcry over civilian casualties in Falluja.
Local doctors reported more than 600 dead in the fighting. Interim Prime Minister Mr Iyad Allawi urged the people of Falluja yesterday to hand over Zarqawi-led militants and seize a "last chance" for peace, but set no deadline. Falluja leaders say they know nothing of Zarqawi's network.
In on-off talks with the government, they have said Iraqi security forces can return to the city, but not US troops.