Iraqi forces are halting their advance on the Islamic State (IS) militants' last urban stronghold of Mosul in order to consolidate gains before striking the fighters, a US military official said Friday.

"They are pausing and repositioning, refitting and doing some back clearing," Colonel John Dorrian, a spokesman for the US-led coalition, told Pentagon reporters via videoconference.

"We think it will just be a couple of days and then we are back on the march toward Mosul. That's their game plan and we believe they will stick to it."