Massive attack on insurgents in Fallujah

Earlier Friday, U.S. planes dropped leaflets urging women children to leave the city, residents said.

As pressure mounted on the guerrilla stronghold, the insurgents struck back, killing one U.S. soldier and wounding five in a rocket attack. Clashes were reported at other checkpoints around the city and in the east and north of Fallujah late in the day.

For the past three nights, long convoys of American soldiers from Baghdad and Baqouba have rolled onto a dust-blown base on the outskirts of Fallujah, a city that has become the symbol of Iraqi resistance. U.S. commanders here have been coordinating plans either to fight their way into the city or isolate it from the rest of Iraq's Sunni Muslim heartland.

If they fight, American troops will face an estimated 3,000 insurgents dug in behind defenses and booby traps. Military planners believe there are about 1,200 hardcore insurgents in Fallujah - at least half of them Iraqis. They are bolstered by insurgent cells with up to 2,000 fighters in the surrounding towns and countryside.

In Brussels, Belgium, Iraq's interim prime minister, Ayad Allawi, warned that the "window is closing" to avert an assault on Fallujah, 40 miles west of the capital. Allawi must give the final go-ahead for the offensive, part of a campaign to curb the insurgency ahead of national elections planned for January.

Sunni clerics have threatened to boycott the election if Fallujah is attacked, and U.N. Secretary-General Kofi Annan has warned U.S., British and Iraqi authorities that a military campaign and "increased insurgent violence" could put elections at risk.

U.S. aircraft struck targets around Fallujah in numerous raids starting late Thursday and continuing into Friday night. Targets included a system of barriers rigged with bombs, a command post, suspected fighting positions and a weapons cache, according to Lt. Nathan Braden of the 1st Marine Division.