Labour leader Andrew Little has made a top secret visit to Iraq to visit New Zealand troops based at Camp Taji and is now questioning whether the two-year term will be extended.
Mr Little has just left Iraq after Camp Taji with Defence Minister Gerry Brownlee and Chief of Defence Force Tim Keating.
Labour opposed the 2015 deployment of troops to help train Iraqi soldiers fight against Islamic State (Isis), but Mr Little said he accepted the invitation from Mr Brownlee because he believed it was important to see first hand the work of the troops and the conditions in which they lived.
Mr Little praised the "skill and professionalism" of the troops he met.
He said it had not changed his mind on opposing the mission, which was based on concerns about the lack of motivation and discipline in the Iraqi Army.
"They are doing an amazing job up there, I don't want to take away from that. I explained to them the reason we didn't support the mission was because we had doubts about the Iraqi Army. I think there are still questions about whether enough has changed in the Iraqi army."
He said the test for that would be whether Iraq was successful in taking back Fallujah and Mosul.
Mr Little said it was obvious the job New Zealand was sent to do would not be completed in two years.
He said American, Australian and Iraqi military had all raised it.
"I do not think it is conceivable that the Government has not been asked to go beyond two years. This is not a two-year programme.
There is a heap of stuff to do. The Government must now be open with the public about the demands being made of it and its plans.
"Prime Minister John Key, who visited Taji last year, said the first review of the deployment showed it was being effective but he had not yet reconsidered the two-year limit."
There has been no request made to us at this time to extend the operation. I haven't seen anything at this point that would indicate to me I would change that position.
"Mr Key said the Government invited Mr Little because he believed it was important that troops serving overseas knew they had wide support in Parliament.
"We believe passionately in the work our men and women are doing in Taji and to us, demonstrating to our servicemen and women that there is widespread parliamentary support is important - far more important than political point scoring over whatever position Andrew Little may have taken."
Mr Brownlee said senior Iraqi commanders had reported that the training had helped regain territory from Islamic State and they intended to return units for further training when possible.
Mr Little will now visit Jordan to visit the Zaatari Refugee Camp, where 80,000 refugees from Syria are living.