AKIPRESS.COM - New Zealand will send troops to Iraq on a 'behind-the-wire" non-combat mission to boost the local military's ability to fight the Islamic State (IS) group, Prime Minister John Key said on Tuesday.

Key said about 140 troops would begin the mission in May after a request from the Iraqi government for international help to increase its military capability against the jihadists, reports AFP.

"We cannot, and should not, fight Iraq's battles for them -- and actually Iraq doesn't want us to," he told parliament.

"Our military can, however, play a part in building the capability and capacity of the Iraqi forces so they can fight ISIL themselves."

Key flagged the mission late last year and it has been hotly debated in New Zealand, with all major opposition parties against it.

A TVNZ opinion poll released this week found 48 percent of participants supported a military training mission, with 42 percent against and the rest undecided.

Key said New Zealand was part of a 62-nation coalition against the Islamic State organisation, also known as ISIL or ISIS, which has captured swathes of territory across Iraq and Syria.

He described the group -- infamous for beheading, stoning and burning alive its victims -- as "barbaric", saying New Zealand would "stand up for what's right".

"Sending our forces to Iraq is not an easy decision but it is the right decision," he said.

He added that New Zealand troops would most likely work alongside their Australian counterparts at a military base in Taji, north of Baghdad.

Key said the initial deployment was for nine months and the mission would not extend beyond two years.