Australia is studying whether to participate in a joint missile defense system with Japan and the United States, partly as a bulwark against regional threats such as nuclear-armed North Korea, its defense minister said Tuesday.

Brendon Nelson, who met with Defense Minister Fumio Kyuma in Tokyo, said the study is only in its initial phase, but options include putting interceptor missiles aboard Aegis destroyers. He added it was too early to talk about timing or costs.

Australia is trying to ramp up its military capabilities and is expanding its military personnel to 30,500 troops from 27,500 as part of an overhaul to take greater responsibility for Asian security, Nelson told a news conference. The upgrade is seen as hinging on Australian coordination with its close allies in Tokyo and Washington.