There are calls for New Zealand to pull its troops from Iraq following the advance of Islamic State militants.

NZ First defence spokesman Ron Mark said the response of Iraqi troops to the Isil advance showed them up as "cowards".

US Defence Secretary Ashton Carter told CNN that Iraqi forces "showed no will to fight" in Ramadi.

"If Iraq hasn't got the will to defend itself then it is not worth one one Kiwi soldier's life," Mark said.

Prime Minister John Key said Tuesday he had no advice that New Zealand troops were in greater danger but would act to protect them if that were the case.

Latest reports say Isil militants have swept through the western Iraqi city of Ramadi, about 100km from the Kiwi base at Camp Taji, and are gaining ground in Syria.

Mark said the Government had sent New Zealand troops on "mission impossible".

The advance of Isil had thrust them to the frontline shielding Iraqi troops.

"Mr Key now has the evidence that the Kiwi training mission is pointless. The Iraqi army cannot be trained. It does not have the will to fight, as American joint chiefs of staff chair General Dempsey pointed out after the Iraqis were routed from the western city of Ramadi, despite outnumbering the enemy 10 to one."

US President Barack Obama has described the losses as a "tactical setback" and said his administration's overall strategy in Iraq and Syria would not change.

New Zealand has a 140-strong contingent in Iraq to train Iraqi forces.

Key said he had checked with New Zealand Defence Force bosses and they advised him there had been no change that would require the withdrawal of New Zealand troops, who do not have a mandate to become involved in combat.

But that situation was under constant review.

"[I am advised] there's no reason to change our thought process on the risks our people face in [Iraq]. It is a difficult environment as we know."

The trigger for a change in stance would be when NZDF believed there was "an absolute threat to our people".

Key would not detail the circumstances that would trigger that change in position.

He is scheduled to travel to Iraq this year to visit troops and he said the Isil advance had not changed those plans.

"Let's put if this way - I don't, but if I had a planned trip there next week I'd go."

Key said the Iraqis had made it clear they were determined to take Ramadi back.

"The only way to do that is to make sure they are equipped and have people that can actually do that job for them and that is why we are training the Iraqi forces."

The world had an obligation to stand up to Isil because the alternative was the murder of civilians.

"I think whats really frightening about IS is the actions that follow when they do get territory and we've seen that with ....400 people being murdered. These people are shocking and we have to stand up to them. "

A decision on whether to act to protect the Kiwi troops would not be based on the proximity of Isil to Taji base, but rather on whether the safety and security of the New Zealanders had been compromised.

"It's about whether we believe the safety and security of our people are compromised. If they are....then we would get them out. The advice we have at the moment is they are totally fine."