Hansen will join the All Blacks after the Six Nations

The 44-year-old will once again team up with former Wales coach Graham Henry, who took over New Zealand when John Mitchell's contract was not renewed.

Joining Hansen as an assistant to Henry is Wayne Smith, who will step down as Northampton coach in May.

"They are both acknowledged as being among the world's finest forwards and back coaches," said Henry.

Smith to leave Northampton

Hansen added: "I am looking forward to working with Graham again and my old mate Wayne Smith."

In the meantime, he will remain in charge of Wales, who look to build on their 23-10 win over Scotland when they face Ireland in Dublin on Sunday.

"Steve Hansen has told me he remains completely focussed and committed to Wales' Six Nations programme," said Welsh Rugby Union chief executive David Moffett.

"The New Zealand post is not something that will be exercising his mind until he returns home.

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"This appointment is not totally unexpected and I am now considering sending an invoice to the NZRFU chief executive Chris Moller on behalf of the WRU for playing this important role in the development of two of their coaches."

Hansen and former All Blacks coach Smith both had coaching roles with the Crusaders at Super 12 level before heading to Britain to further their careers.

"I have worked with Steve and Wayne in the past in a variety of capacities and found them to be up with the best technical and man management coaches in the game," added Henry.

Wales have yet to name a successor to Hansen while Ulster coach Alan Solomons will replace Smith at Northampton.

"It's a dream to have another opportunity to coach the All Blacks," Smith told the Dominion Post newspaper.