The Government has made the "difficult" decision to send Special Air Services (SAS) troops back to Afghanistan, Prime Minister John Key announced today.
The deployment will be the fourth of SAS troops, and a commitment has been made to maintain about 70 personnel for up to 18 months, in three rotations.
"It's a difficult decision. There's no getting away from the fact that Afghanistan is a dangerous place," Mr Key said.
He said the deployment would be in the "foreseeable future" but kept with convention in refusing to say when, or where, the elite troops would go.
Parallel to the SAS deployment would be the gradual withdrawal of the Defence Force's 140-strong provincial reconstruction team (PRT), which has been in Bamyan province since 2003.
The PRT would be withdrawn during the next three to five years and by the time it left, New Zealand would have had a presence in Afghanistan for 14 years.
Afghanistan remained an unstable place but Mr Key did not believe it was any more dangerous now than during previous SAS deployments.
"I don't think you can eliminate that there is a real risk to the people that we're deploying there, just as there actually is, I think, quite a significant risk to the 140 personnel that we have in Bamyan Province," he said.
"But I wouldn't call, on the advice that I have, the likelihood that this rotation could be more dangerous than previous rotations, not withstanding that Afghanistan is an increasingly dangerous place."
The United States had made repeated requests for the SAS to return to Afghanistan.
Mr Key met a senior US representative at last week's Pacific Islands Forum and "gave them an indication that it was likely this decision would be reached".
"I think that they are supportive, obviously, and grateful that New Zealand is playing its part."
The Green Party has raised concerns in Parliament about the controversial handing over in 2002 of Afghan prisoners by New Zealand troops to US forces who allegedly mistreated them.
Mr Key today said the SAS would be most likely to hand any detainees over to Afghan authorities.
"Like New Zealand, Afghanistan is a party to the Geneva Convention," he said.
"New Zealand has already received an assurance from the Afghan government that all transferred detainees will be treated humanely according to these conventions and international law."
Mr Key also announced today there would be greater New Zealand civilian involvement in Afghanistan, particularly in agriculture, health and education sectors.
An ambassador would be appointed to support that work, based in Kabul.
Labour leader Phil Goff said his party did not support the SAS deployment as it believed the way to win the conflict was by winning over the people "and we were doing that most competently and effectively through the PRT in Bamyan".
"The concerns that we have with the SAS don't relate to the competency of the SAS itself but rather what it requires to win this conflict at the present time," he said.
"We are not in the situation we were in earlier in the 21st century where this was a battle with al Qaeda. This has fast moved in the direction of being a civil war."
Green MP Kennedy Graham said the decision was an example of "strategic folly based on muddled thinking".
"The engagement of our SAS will compromise the legitimacy and the effectiveness of the work done by our (PRT)," Dr Graham said.
The way forward was through the PRT and increased civilian aid, not by sending "crack combat troops to engage in covert counter-terrorism activities there".