The 1,000 U.S. soldiers who parachuted into northern Iraq's mountainous Kurdish enclave spent Thursday preparing the airstrip for the arrival of more troops and equipment.

The Iraqi Kurds hope the arrival of the Americans is the start of the long-awaited northern front. But it's clear coalition forces will be needed in far greater numbers in the coming days if they're to be anything more than a stabilizing force in the Kurdish enclave.

Hoshyar Zebari, a senior Kurdish official, says a lot more soldiers and equipment will be needed to take on the nearly 100,000 Iraqi regular forces. Zebari also says the fight in the north won't be like the operations in the south.

"These troops may be injected behind enemy lines to do operations behind those lines," he said.

U.S. warplanes have been hitting Iraqi positions with intensity all along the front between Iraqi- and Kurdish-controlled territory over the past 48 hours.

Kurdish soldiers, known as peshmerga, say some Iraqi units have pulled back. They also made a small incursion into Iraqi territory.

On Thursday, near Chamchamal, Kurdish soldiers moved a few kilometres into Iraqi territory occupying positions abandoned by the Iraqi forces.

Washington has been leery of Kurdish participation, fearing it will anger Turkey. But Zebari insists the Americans will need Kurdish help.

The Kurds say they have covert networks already inside Iraqi cities like Mosul and Kirkuk ready to rise up against the Baghdad regime.

"The opposition knows the people better than the (U.S.) 4th Infantry Division (knows them) and what kind of resistance they are encountering. This is not a technical war. You can destroy positions from the air but when it comes to real battles and confrontation you need people on the ground to take up resistance," said Zebari.

There have also been reports of defections – 16 at Kurdish bases on Thursday. Kurdish officials say that brings the overall total in the north to more than 300.