Australia could face a growing threat from large nations with huge populations but diminishing food and resources, a new study warns.

Strategic analyst Dr Robert O'Neill said those threats could be akin to those which confronted weaker states in the 18th and 19th centuries.

He said Australia could not prevent such a threat but could make it too difficult for a potential aggressor to act.

In the paper, released by the Australian National University Strategic and Defence Studies Centre, Dr O'Neill said successive defence white papers stressed that the most basic defence job was to defend Australian territory.

Although only once, in 1942, was Australian sovereignty actually under threat, ''the nature of world politics is changing, however, and international society in the 21st century could prove to be dangerous for a large well-endowed but sparsely populated country like Australia''.

Dr O'Neill said Australia needed substantial air and naval forces, which would be expensive.

AAP