The Treaty of Amity and Cooperation in Southeast Asia was signed in 1976 by five countries, members of the Association of Southeast Asian Nations (ASEAN): Indonesia, Malaysia, the Philippines, Singapore and Thailand.
At present, the parties to the Treaty also are: Australia, Bangladesh, China, East Timor, France, India, Japan, Democratic People's Republic of Korea, the Republic of Korea, Mongolia, New Zealand, Pakistan, Papua New Guinea, Sri Lanka, Turkey, the US and (since 2004) Russia.
The Treaty has established itself as an important international legal instrument that facilitates the development of multilateral cooperation in the Asia-Pacific region in the political, economic, social, scientific, technical, and humanitarian spheres.
Given the increasingly important role played by multilateral organisations and entities in political and economic processes in the Asia-Pacific region, it was considered opportune to amend the Treaty to permit regional organisations to accede to it. This provision is contained in the Third Protocol, which was signed by the foreign ministers of parties to the Treaty on July 23, 2010 in Hanoi.