"Our troop deployment does begin today along with the Australian."
Mr Soper said it was likely that the two-year timeline would be "renegotiated" as the deadline for pulling out approached.
"Whenever troops are sent abroad they're often gone for much longer than the government intended them to be."
In announcing the deployment in February, Prime Minister John Key said the New Zealanders would work "behind the wire" in a training capacity with Iraqi Security Forces.
He said troops were likely to arrive in the Taji military complex north of Baghdad in May, and the deployment would be reviewed after nine months.
Chief of Defence Force Tim Keating said in February that the troops would be working alongside the Australian Defence Force, providing training to Iraqi security forces in combat skills needed to roll back the Islamic State threat.
The deployment at Taji would include 106 personnel, with a further 37 at other locations in the Middle East.