"There is a huge number of IEDs [improvised explosive devices] and mines around the place and the casualty rate, particularly amongst kids, is very high indeed.
"We have committed to doing some demining work as that becomes available."
New Zealand is considered an expert on mining deactivation, which is mostly carried out by former soldiers. It has previously worked in Colombia, Cambodia, Laos and Palestine.
The Defence Force began training local police last year, who would be working in areas liberated from Isis.
They would soon begin helping with tasks such as restoring courts and public administration services.
Around 100 New Zealand troops are already stationed at Camp Taji, 50km from Baghdad, where they have been training Iraqi forces and providing intelligence.
McCully said New Zealand's aim was always to match its military contribution with a humanitarian contribution.
Discussion at the counter-Isis talks also focused on ensuring that Isis did not find a safe haven in other countries after it lost its strongholds in Iraq and Syria.
McCully said New Zealand would be working closely with South East Asian countries, which were expected to see rising numbers of foreign fighters return home after fighting with Isis.
Its support for those countries would mostly consist of intelligence and information-sharing, McCully said.
TRUMP'S RIGHT HAND MAN
Tillerson is the first Secretary of State in modern history with no experience of public office.
He joined ExxonMobil in 1975 as a production engineer and became the company's chairman and chief executive in 2006.
McCully sat next to him during lunch in Washington, and said he was a "completely different personality" to his predecessor John Kerry.
Tillerson was "very professional but very personable", McCully said.
"You don't get to be the head of Exxon without being a hugely capable and intelligent person."
New Zealand's Ambassador to the US, Tim Groser, posted a photo of McCully and Tillerson on Twitter.
Ahead of his attendance at the meeting, McCully said defeating Isis was "more than a military campaign".
"The coalition will review progress across all lines of effort, including the important work being done to undermine Isil's propaganda and cut off its finances.
"As Isil finds itself on the back foot in Iraq and Syria, we want to work with our Coalition partners to ensure that Isil does not find safe haven elsewhere."
New Zealand has contributed about $26 million since 2012 in humanitarian assistance for people caught up in violence in Syria and Iraq.
