Wellington - Japan assistant coach Tony Brown has rejected approaches from two leading contenders to replace Steve Hansen at the All Blacks, saying he will only go if Brave Blossoms head coach Jamie Joseph gets the job.

Joseph, who took Japan to an historic quarter-final berth at the Rugby World Cup, has not publicly confirmed if he will apply for Hansen's job and Brown said the pair want to coach the All Blacks "when the time is right".

New Zealand Rugby officially launched its search for a new coach on Wednesday with the appointment to be made before Christmas.

Chairperson Brent Impey said a "small group of coaches familiar with New Zealand's professional rugby environment" have already been invited to apply.

Brown told Sky TV's "Breakdown" programme in New Zealand that he had turned down approaches to link up with current All Blacks assistant Ian Foster and triple Super Rugby champion coach Scott Robertson from the Crusaders.

"I made a decision I'm going to stay with Jamie. If he applies for the All Blacks, I'm in. If he stays with Japan, I'm in," Brown said as speculation mounted over who will replace Hansen who stepped down from the post after New Zealand finished third at the World Cup.

Brown, a former All Blacks flyhalf, has formed a close bond with Joseph ever since the pair turned an ailing Highlanders side into Super Rugby champions in 2015 and then lifted recent World Cup hosts Japan into a top-10 nation.

"It felt right to stick with Jamie and what we've been doing for the last eight years," Brown said.

"It was a massive decision. One hundred percent I want to coach the All Blacks tomorrow. But it didn't feel right floating between three different coaching teams where I don't get a say.

"Jamie puts together a great team and we're all trying to make the team better. That's what I like about Jamie... Everyone's trying to make the team better.

"We both want to coach the All Blacks but we both want to do it at the right time. Whether the right time is now, I hope it is or it may not be, it may be in four years."

Meanwhile, All Blacks fullback Beauden Barrett is backing Foster to take over from Steve Hansen, arguing that the role needs "continuity".

Candidates for the position will be interviewed by a five-person panel which includes former World Cup winning All Blacks coach Graham Henry.