Prime Minister Scott Morrison announced a plan worth more than half a billion US dollars to revamp four military training facilities in the remote north over the next five years.

The package of upgrades is more extensive and more costly than first conceived two years ago and would allow more joint drills with American forces, including US marines rotating through the northern port of Darwin.

"We will always do what is necessary to ensure Australia has the capability it needs to protect and defend its interests," Morrison said Wednesday.

His conservative government has sounded a more hawkish tone on defence matters in recent months, as relations with China have soured.

Last year, the Morrison government unveiled plans to dramatically tool up its military with high-tech weaponry in the face of greater perceived threats from Beijing.

Defence experts have even suggested the country should consider developing nuclear weapons capability, because Australia's relative small conventional forces are unlikely to be able to defend the vast continent-country from an attack.

This week, a top government official warned that free nations "again hear" the "drums of war" in the region and newly installed Defence Minister Peter Dutton openly mused about the prospect of a war between China and Taiwan.

Critics have accused the government of manufacturing a crisis to divert attention from a stalled coronavirus vaccine rollout and sliding poll numbers.

Former prime minister Kevin Rudd said Morrison, Dutton and allied media mogul Rupert Murdoch were "trying desperately to shift the domestic political agenda away from the vaccine debacle, the climate change fiasco and abuse scandals in Canberra".