Australia has been debating whether to install a missile defence shield to protect the country's north following the growing threat of a strike from North Korea.
The leading calls have come from Australia's two former prime ministers, Mr Tony Abbott and Mr Kevin Rudd, who said the nation needs an anti-ballistic missile system.
The calls followed North Korea's expanding missile programme and its threat to Australia in April to stop "blindly and zealously toeing the US line" or it would consider launching a nuclear strike.
Experts believe North Korea's latest intercontinental ballistic missiles (ICBMs) could - when completed - reach northern Australia, which is sparsely populated but includes the city of Darwin, where US Marines are based.
Mr Abbott, a former Liberal PM, said Australia should be "urgently investing in upgraded missile defences".
"Of course, we should be able to defend ourselves if they have missiles that can reach Australia," he told Fairfax Media last Thursday.
This followed a similar call from Mr Rudd, a former Labor PM, who said Australia should "begin analysing ballistic missile defence needs, available technologies and possible deployment feasibility for northern Australia".
But Prime Minister Malcolm Turnbull has resisted the calls, saying an anti-missile system such as the Terminal High Altitude Area Defence system was not designed to thwart long-range weapons or to protect a vast area such as northern Australia.
Defence Industry Minister Christopher Pyne dismissed the calls for a missile shield as "patently absurd". He said it would be too expensive and would not protect against ICBMs.
"It would be tens of billions of dollars and take many years to replicate what the United States has done for continental US," he told ABC News on Monday.
Most experts agreed that a missile shield was impractical.
Dr Andrew Davies, director of the Defence and Strategy Programme at the Australian Strategic Policy Institute, said it was "silly" to seek a missile defence shield. He told The Straits Times: "The only workable missile defence systems are against short-range missiles, where the trajectories are not as high and the terminal velocities are not as fast (as intercontinental missiles)."
Dr Alexey Muraviev, a security expert at Curtin University, said building a defence shield was costly and would be considered "threatening" by China as well as North Korea.
Some analysts have been more supportive of a defence shield.
"Given that China probably won't move to tighten sanctions, it has to be about missile defence," Associate Professor Robert Kelly, from Pusan National University in South Korea, told Fairfax Media in July.
Even if such a shield was possible, Dr Muraviev said, there may not be time to build it."The (shield) may not arrive in time and would not be operational in time for the current threat from Pyongyang."
