"This is it, the last push," said Major Maurice Goins before the attack near the Shiite Muslim holy city of Karbala, some 80 kilometers (50 miles) south of Baghdad.

Members of the 3rd Infantry Division met only "disorganised" resistance, said Colonel Will Grimsley, commander of the division's first brigade.

It was not clear whether any of Iraq's elite Republican Guard were involved in the resistance. Elements of the Guard's Medina armoured division and other units had earlier been reported lying in wait in the area but apparently failed to engage in combat.

"It's much less worrying now we are through the gap," Grimsley said as the troops continued their push north after crossing between the city and a nearby lake.

At least a dozen prisoners of war could be seen huddled to the ground guarded by US soldiers as a convoy passed through the gap in an operation which began shortly after midnight (2100 GMT Tuesday).

SPACE.WIRE