Defence Minister Jonathan Coleman is defending a new battle training facility for New Zealand elite troops as "absolutely necessary".
The Defence Force wants the multimillion-dollar base at Ardmore in South Auckland to be operating by 2015.
It is looking internationally for a designer and has disclosed details about what it wants for the training facility for the SAS.
The design brief says the building must cater for simulated explosions and 360-degree live weapon firing on multiple levels.
The indoor-outdoor facility would also be able to simulate exercises on ships, aircraft, buses, trains or oil rigs with vehicle, foot and air assaults.
Designers must also consider how external shooters could fire into the building for training purposes.
Dr Coleman maintains the base is needed, despite the SAS not having any future deployments.
"The project is absolutely necessary, because when the SAS is called upon - and we never know when or why that would be - these guys have got to be absolutely at the peak of their training. So they do need a facility like this to make sure they're properly prepared."
Dr Coleman will not say how much the facility will cost, citing commercial sensitivity.