Defence shield: 'It can't be off a shelf'

Buying a defence missile shield to protect Australia from North Korean intercontinental ballistic missiles is more complicated than grocery shopping, the federal government warns.

Former prime ministers Kevin Rudd and Tony Abbott have called for Australia to get a shield, similar to America's THAAD system.

But Defence Industry Minister Christopher Pyne shot down the prospects of acquiring a system as he toured defence contractor Raytheon Australia in Canberra on Monday.

It would potentially take seven to 10 years to build and cost in the tens of billions of dollars, he said.

The government earlier this year commissioned Raytheon to develop a short-range system to protect deployed troops at the cost of more than $1 billion.

But Mr Pyne said if the government did invest in a longer-range system it would be at the expense of other defence investments.

"Saying we need an intercontinental ballistic missiles defence shield is an easy thing to say," Mr Pyne told reporters.

"It's not like heading down to Woolworths and purchasing it off the shelf."

Mr Pyne insisted the threat posed by North Korea was not at a point where he was receiving advice the government needed to change its military investment plans.

Over the weekend, North Korea fired three short range ballistic missiles into the Sea of Japan which travelled about 250km.

Mr Pyne cut a virtual ribbon for Raytheon Australia's whizz bang 320-degree cave of 72 screens.

He donned 3D nerd glasses and used a laser controller inside the cave, road testing the virtual reality system that brings designs to life so changes can be made before equipment is built.