New Zealand's troops in Afghanistan are "highly likely" to return home in April, but their withdrawal depends on negotiations with a coalition partner, Prime Minister John Key says.
Three members of the Provincial Reconstruction Team (PRT) - Lance Corporal Jacinda Baker, 26, Corporal Luke Tamatea, 31, and Private Richard Harris, 21 - were killed instantly on Sunday when their Humvee hit a roadside bomb, just two weeks after two others died in a firefight with insurgents.
They were in the last vehicle of a convoy of four Humvees taking an ill patrol member to the doctor when they hit the bomb.
Mr Key says their deaths will not speed up New Zealand's planned withdrawal from Afghanistan next year - but on Monday afternoon, for the first time, he cited April as the most likely time for the withdrawal.
The only other option is in September next year, which he says is "the worst-case scenario".
Mr Key would not say why those months were the only options, but said the withdrawal relies on "the logistics of a number of things that are happening there in terms of the way that we work with our partners".
"It's also a scaled transition, so it's not quite as straightforward as saying everything happens on one particular date - there are some reasons why we don't necessarily want to go through all of that publicly," he told media.
Foreign Affairs Minister Murray McCully announced in May the PRT would be withdrawn "later in 2013", and Mr Key was unable to say why the proposed date had changed.
"We're still, we think, about two weeks away from making that final decision," he said, adding that the logistics are "contingent on some work (with) one of our partners".
"We've been going back and forth with that particular party to see whether there's flexibility in the way that they operate, and that's been an ongoing dialogue, where we've put up lots of different options to try and understand what their preference is.
"Essentially the advice we've had from that coalition partner is that there's no flexibility with what they're doing," Mr Key said.
He was uncertain about whether he could publicly name the coalition partner involved in the negotiations.
Mr Key also said it is likely a logistics expert from the elite SAS will be deployed to Afghanistan to assist the PRT with its planning, but there are no plans to redeploy SAS combat troops.
The bodies of the dead soldiers are expected to be flown to Australia by the Australian Defence Force before arriving back in New Zealand on Friday.
Mr Key will attend their funerals, which he believes will be held before he attends the Pacific Islands Forum in Rarotonga next Wednesday.