Australia’s unofficial treaties. There are many reasons Australia

Australia's defence and peace time alliances
Australia is involved in many official an unofficial treaties. There are many reasons Australia gets in to treaties. Also many responsibilities and consequences for Australia that come with these treaties.
ANZUS treaty (Australia New Zealand United States Treaty)
This treaty was sighed by the three parties on the 1st of September 1951 in San Francisco and was brought in to force on the 29th of April 1952
This is a treaty between New Zealand Australia and America concerning the pacific area. This treaty basically states the all parties involved will help in conjunction with each other and individually to keep peace in the Pacific Rim.
It also has the purpose of declaring publicly and officially that none of the three parties stand alone in the pacific. The treaty also recognizes that even though Australia and New Zealand are part of the British Commonwealth they have "military obligations" in side and out side the Pacific Rim.
The conditions of this treaty are that all the three nations defend one another's Pacific Rim territory. This includes all islands under any of the countries jurisdictions inside the pacific rim, any of the countries armed forces or any of the counties public vessels or aircraft.
America suspended its obligations to New Zealand under this treaty on the 11th of august 1986. Because New Zealand would not let America's military vessels in to its harbours. New Zealand's reason for doing this was that America would not declare that it's ships where not nuclear.
ASEAN (Association of South East Asian Nations)
ASEAN is a regional forum. The forum was established in 1994 and draws together 23 countries, which have an impact on the security of the pacific region. These countries include ten ASEAN member states Brunei, Burma, Cambodia, Indonesia, Laos, Malaysia, Philippines, Singapore