New Zealand has congratulated Iraq and pledged more funding after Isis forces were defeated in the city of Mosul - and Prime Minister Bill English has not ruled out further help.

Iraqi Prime Minister Haider al-Abadi is now in Mosul and has congratulated armed forces for their "victory" over Isis, after nearly nine months of fighting in the city.

Asked if New Zealand could help with any reconstruction or efforts to clear mines in Mosul, English said that was "always possible" but no request had been received yet.

"I think there is a wee way to go yet just to exactly settle down what appears to be a very recent victory for the Iraqi government. We have a presence there, and we'd of course work with them to contribute what we can."

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Foreign Minister Gerry Brownlee said the city's capture was an important milestone.

"Losing the symbolic heartland of its so-called caliphate in Iraq will serve as a severe blow to Isis fighters and its supporters around the globe."

Brownlee said a further $1.4 million contribution would be made through NZ Aid to the United Nations Funding Facility For Immediate Stabilisation.

"New Zealand remains committed to coalition efforts. Now is the time to demonstrate to Isis, through our ongoing commitment, that Iraq and the global coalition are dedicated to defeating the terrorist threat."

The defeat of Isis in Mosul comes three years after the militants took the city. The United Nations predicts it will cost more than US$1 billion to repair basic infrastructure in Mosul.

New Zealand troops have been based in Iraq and Camp Taji, just outside of Baghdad, as part of a joint mission with Australia to train members of the Iraqi Security Force.

Last year the Government announced it was extending the deployment by 18 months, until November 2018.