US marines prepared on Friday to storm the Iraqi cities of Fallujah and Ramadi to crush Sunni Muslim insurgents and Arab fighters.
"We are gearing up for a major operation," Brigadier General Denis Hajlik told reporters at a base near Fallujah. "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 nation-wide 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.
Interim Prime Minister Iyad Allawi urged the people of Fallujah on Thursday to hand over Zarqawi-led militants and seize a "last chance" for peace, but set no deadline.
Zarqawi's al Qaeda-allied group threatened on Tuesday to behead a Japanese hostage within 48 hours unless Tokyo withdrew its 550 non-combat troops from Iraq. Japan rejected the demand.
MYSTERY BODY: The deadline passed without any firm word on the fate of 24-year-old traveller Shosei Koda. Police said they had found the body of an unidentified Asian in Tikrit, Saddam Hussein's home-town, on Thursday, but its description did not fit Koda.
Gunmen killed the driver of a Turkish truck in the northern city of Mosul on Friday and set it ablaze, witnesses said. It was not immediately clear if the driver was a Turk, but the truck, carrying bottled water, had Turkish plates and markings.
A car bomb blew up near a US convoy in southern Mosul, killing an Iraqi civilian and wounding three, hospital staff said. The US military said two soldiers were slightly hurt.
Three American soldiers were wounded when a roadside bomb blast hit their Humvee vehicle on a highway between Mosul and Tel Afar 60km to the west, the military said.
Assassins killed Aqil Hamed al-Adeli, deputy governor of Diyala province, north-east of Baghdad, police said.
Gunmen shot dead two policemen in Latifiya, just south of Baghdad, as they were driving from Baghdad to their posts in the Shia city of Kerbala, police in Kerbala said.