Labour leader Andrew Little said Labour would support sending SAS troops to fight Isis if the right conditions were met.
Those conditions were having a clear and realistic objective, that it would have to be part of a multinational mission mandated by the United Nations and that the level of risk needed to be acceptable.
"Troops on ground as part of a multinational force, targeting those areas where Isis has a stronghold and those areas where they have seized oil refineries and those sorts of things to defeat them in those sorts of areas - it is going to take more than just air strikes," he said.
Asked if that meant he thought there was a place for troops on the ground with the stipulated conditions he said: Yes. If they are in the right place, properly mandated, and with a realistic objective then yes there is."
He also said there had to be a consensus between the United States and Russia before any intervention would be effective.
Mr Little was speaking to the Herald from Washington DC where is on an official visit as
With the support of the Ministry of Foreign Affairs and Trade staff, he is meeting officials from the Pentagon and State Department and representatives on Capitol Hill.
The main subjects of discussion are international security and the Trans Pacific Partnership trade deal, reached in October among 12 countries including the US and New Zealand.
New Zealand Prime Minister John Key announced in February that New Zealand would deploy about 140 troops to Iraq for two years to run a training mission with Australia to rain Iraqi troops to fight Isis (also known as Daesh).
The deployment did not require a vote of the Parliament, which is just as well for Mr Key because after the Northland byelection changed the make-up of Parliament, a majority of the Parliament did not support the deployment.
Defence Minister Gerry Brownlee announced last week that US Defence Secretary Ash Carter had written to New Zealand, among other countries to seek a bigger contribution, including the possibly of sending special forces.
Mr Key said the Government would take some time to consider the request but his gut feeling was that the current contribute was enough.
However it will feature in the work of the cabinet early next year, along with a review of the Camp Taji training mission, and a SAS mission could find cross-party support.
"We just didn't think sending trainers to support the Iraqi Army looked like anywhere near dealing with the issue," Mr Little said. "So now that there is a renewed international tension on the damage Isis is doing and can do, obviously we would want to play our part but it has got to be properly mandated and it has got to be a mission with a realistic objective, focused in the right part of the world."
The focus at the moment was on air strikes but that could be too crude a response.
"That was France's initial response after the Paris attacks but we know from that that are potentially significant civilian casualties as well."
He did not believe that the resolution passed on November 20 by the UN Security Council - after attacks in Paris, Beirut, Tunisia, and Turkey and the downing of a Russian passenger plane over the Sinai - could be seen as a UN mandate for a multinational force against Isis.
"I didn't see it as a UN mandated mission and if it is going to be done properly, it is going to require coordination between whatever contributing states are involved and a proper mission with a set of objectives ... to have the best chance of achieving the goal of defeating Daesh wherever they are, particularly in Syria."
The UN motion described Isis as "a global and unprecedented threat to international peace and security" and called on member states "to eradicate the safe haven they have established over significant parts of Iraq and Syria."