Australia must develop greater missile defences to ward off a strike from North Korea, a former high-ranking Pentagon official said.

Key points: Australia could be struck by a North Korean weapon, Dr Roberts warns

Australia could be struck by a North Korean weapon, Dr Roberts warns He says separating US allies from the US and from each other is central to Mr Kim's strategy

He says separating US allies from the US and from each other is central to Mr Kim's strategy Australia must ensure warships are equipped with advanced defences, Dr Roberts says

Brad Roberts served as US deputy assistant secretary of defence for nuclear and missile defence policy between 2009 and 2013, and is currently in Australia briefing senior officials about regional dangers.

He warned Australia could be struck by a North Korean weapon.

Dr Brad Roberts is in Australia to brief senior officials about regional dangers. ( Supplied )

"Unfortunately, Australia doesn't really get to choose whether or not North Korea threatens it — it's the choice that the North Korean leader [Kim Jong-un] makes," he said.

Dr Roberts said it was very clear separating US allies from the US and from each other is central to Mr Kim's strategy.

"He does this by threatening them and presenting to our publics an image of great vulnerability and great cost if there were war," Dr Roberts said.

"His objective is to make us fearful so that our leaders will not stand up to his threats and coercion."

Dr Roberts, who led the Obama administration's Nuclear Posture Review and Ballistic Missile Defence Review, does not believe Australia needs to adopt an American-style expensive land-based missile shield, but said it must ensure warships are equipped with advanced defences.

"I don't think it's a large number of very expensive interceptors and radars deployed around the periphery of the Australian continent," he said.

"A sea-based capability on the advanced destroyer that would include a sea-based radar and some interceptors: that could operate in coalition partnership with other allies."

US President Donald Trump is locked in a war of words with North Korea, which has said Mr Trump's threat to "totally destroy" the hermit kingdom amounts to a declaration of war.

Last month, North Korea's official news agency said the Australian Government should be focused on maintaining the peace of its own country, instead of joining the US in moves towards nuclear war.

Prime Minister Malcolm Turnbull hit back at "reckless" North Korea after the reclusive country described Australia's decision to participate in joint military exercises with the US and South Korea as a "suicidal act".

Defence Industry Minister Christopher Pyne confirmed the Government was considering upgrading the Navy's new air warfare destroyers to include missile defence shields after "very irregular behaviour" by North Korea.

"In the Defence White Paper, and the integrated investment plan, upgrades of the warfare destroyer capabilities have been already flagged," Mr Pyne said.