By Dumeetha Luthra
BBC correspondent in Irbil
American special forces and Kurdish fighters are closing in on the cities of Kirkuk and Mosul in northern Iraq.
Kurdish officials say their forces are just five kilometres (three miles) from the strategic oil city of Kirkuk and less than 40km (25 miles) from Mosul.
Mosul came under heavy aerial bombardment on Monday, although there have been US air strikes along the entire front line separating Iraq from the Kurdish-controlled area.
The plan of forcing the Iraqi army to retreat as a result of air power alone appears to be working.
The special forces and Kurdish soldiers have occupied swathes of territory running along the former front line between the Kurdish-run enclave and land controlled by the Iraqi army, and are pushing towards the region's major oilfields.
Both Mosul and Kirkuk are major strategic towns for the US-led coalition to take.
But on the ground, the Americans and Kurds have met heavy and unexpected resistance.
Although the Iraqis are moving back and reinforcing around Kirkuk and Mosul, they continue to shell the coalition troops.
Soldiers say the Iraqi army are mixing with villagers to avoid being targeted by air strikes.
One special forces soldier said it meant that the whole process was taking much longer than expected in northern Iraq.