Islamist war could last a century: Leahy

Australia is involved in what could be a century-long conflict against radical Islam but should try to avoid direct combat, a new reports says.

Former army chief Peter Leahy says Australia should not sit idly by but there are limits to what it can do.

"Australia's international focus should be on co-operating with allies and friends to support moderate nations with radical Islamist problems in the immediate region: Indonesia, the Philippines and Pakistan," he says in the report.

Professor Leahy, the director of the Canberra University National Security Institute, says the threat from radical Islamists is real, likely to be sustained and a threat to Australia's way of life.

The home-grown terrorism threat would worsen and there was real potential for attacks.

But Australia should try to avoid involvement in fighting the extremists because this was the responsibility of regional nations.

"The best course of action is to be careful about becoming involved and to offer carefully tailored, largely non-combat support where appropriate," he says in the paper, which was released by the Australian Strategic Policy Institute.

Prof Leahy says defensive measures are important but so is an offensive capability to reach out to deter and if necessary destroy imminent threats.

"The focus should be on defensive and protective measures and intervention only when there's a clear vision of what can be achieved, an agreed and long-term strategy, and the commitment of resources over an extended period," he says.