In a strongly worded statement issued by the US, Japan and South Korea, the three nations said they would never accept a nuclear-armed North Korea and said the rogue state should return to the negotiating table.

Asked on Friday about acquiring a missile defence system, Mr Turnbull said the Australia's focus was on protecting deployed forces in the field and that the answer to the North Korean threat was the denuclearisation of North Korea.

"We are examining missile defence, in fact, we're developing missile defences as you know, as you would've seen in our Defence White Paper. The focus is on protecting our forces both at sea and on the ground – our deployed forces in the field," he said.

Mr Rudd's comments referred to the need for a system that would protect population centres such as Darwin – which is now potentially within range of North Korea's missiles – rather than the systems Mr Turnbull referred to.

"In terms of a missile defence shield for Australia overall, I know there has been some and you would've seen some briefings given in Australia while I've been away, there has been talk about the THAAD system – that's not really suitable for our situation – but I can assure you that we are constantly examining how we can ensure that Australians are safe," he said.