A security expert says if New Zealand special forces are in Iraq it would be an instance of intervention by stealth.

The Government is denying it but The Guardian has reported our SAS are in northern Iraq alongside British and Australian soldiers, and calling in air strikes targeting Islamic State.

READ MORE: SAS not in Iraq- Brownlee

Otago University director of the National Centre for Peace and Conflict studies Professor Kevin Clements says the probability of mission creep developing into a combat role was what they argued about when the special training mission to Iraq was announced.

He says its dangerous because there is no guarantee that the Mosul intervention is going to be successful.

"I think past experience in Iraq shows that most of the foreign interveners do not come out covered in glory, they come out with very damaged reputations."

Professor Clements said they were concerned about the air strikes targeting Islamic State.

"Most of us argued that there was the probability of mission creep and developing a combat role and I think that's exactly what happened. I think it would be an instance of intervention by stealth."