John Key has revealed he considered sending the Special Air Service, or SAS, to Iraq instead of extending the military trainers' deployment.
The SAS is New Zealand's most elite military unit, and Mr Key said the United States has specifically asked for its elite troops in the fight against Islamic State.
He said all options were on the table as the Government looked at what to do in Iraq.
"[The SAS] could have gone there in a training role or other roles, and at the moment we don't think that is appropriate," Mr Key said.
"We looked at the range of possibilities, of which that was just one, and measured that against the possibility of doing nothing, pulling people out and saying 'that's enough'.
"I just took the view that we needed to do a bit more. I accepted that some people would criticise me for that but I think in the end I can't let the fact that we are staying a bit longer than we originally thought make me make a decision which would be a purely thought out decision of putting people in harm's way. Better to take whatever flak comes my way of extending their mission."
Instead of sending in the SAS, Mr Key opted to keep the 143 Kiwi personnel in Iraq until the end of 2018.
Asked if he would rule out sending in the SAS in the future, Mr Key said: "I've learnt the hard way not to make blanket statements".