Near Fallujah, Nov 6, SPA -- Long convoys of American soldiers rolled onto a dust-blown base on the outskirts of Fallujah as U.S. warplanes intensified attacks in preparation for a wider assault on the city, a symbol of Iraqi resistance. More than 10,000 American soldiers and Marines massed for an expected offensive, and Iraq's prime minister warned the "window is closing" to avert an attack. U.S. planes dropped five 500-pound bombs at several targets in Fallujah early Saturday, including a factory as well as suspected weapons caches. The drone of U.S. aircraft heading toward Fallujah could be heard over Baghdad. The U.S. military said the main highway into Fallujah has now been completely sealed off. Residents reached by telephone Friday said the air raids were the most intense in months, and that, as well as bombs, U.S. planes dropped leaflets urging women and children to leave Fallujah, a city of some 300,000 people 40 miles west of Baghdad. 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. An AC-130 gunship fired at several targets as U.S. forces skirmished with insurgents, the Army said.--MORE1258 Local Time 0958 GMT www.spa.gov.sa/215692