TOKYO : Australia is studying whether to participate in a joint missile defence system with Japan and the United States to guard against regional threats.

This was according to its Defence Minister, Brendan Nelson, who spoke to reporters in Tokyo.

He said Australia is in the process of building its military capability and wants to step up its security alliance with Japan.

Australia is building up its military capabilities, so it can play a bigger security role in Asia.

It plans to expand its troops by about a tenth, from the current 27,500 to 30,500.

The country will also acquire three advanced anti-warfare destroyers.

Mr Nelson hinted at the possibility of equipping Australian military ships with missile defence capabilities.

He said: "Australia has not yet made a decision and it will be sometime before we do so, as to whether or not we would put on to them for example an SM3 missile which would be a part of a mobile anti-ballistic missile defence capability. Our position is that we support what Japan and the United States are jointly doing for specific threats that might be in the region, and in a very limited way we are studying the extent to which we might also be able to in the future provide assistance in that regard."

The move is in response to heightened concerns about possible attacks by terrorists and extremist groups.

And according to Mr Nelson, North Korea's nuclear ambitions are not just a threat to East Asia, but also Australia.

He said: "For the Japanese people especially, but for all of us who live in this region, the threat presented by North Korea with its Taepodong 2 launch in July and its nuclear detonation in October last year is real and needs to be dealt with, with all of the diplomatic force that we can apply."

It is believed that the Taepodong 2 can reach as far as Australia.

Minister Nelson spoke ahead of a crucial joint Japan-Australia foreign and defence ministerial meeting on Wednesday.

It is based on a joint security declaration signed between Japanese Prime Minister Shinzo Abe and Australian Prime Minister John Howard in March.

Australia considers Japan an important ally.

And during Mr Nelson's visit, both sides hope to produce a framework for closer cooperation on issues like security, peacekeeping efforts, counter-terrorism and disaster-response. - CNA/ch