The Regional Comprehensive Economic Partnership, or RCEP, is set to take effect in January now that Australia and New Zealand have completed approval procedures to join the pact.
The two countries issued separate statements on Tuesday.
The deal was signed last November by Japan, China, South Korea, Australia, and New Zealand, along with the 10 members of the Association of Southeast Asian Nations. Domestic procedures are under way in countries which have yet to approve the pact.
RCEP will take effect 60 days after a minimum of six ASEAN members and three non-ASEAN signatories ratify the agreement.
RCEP will be the world's largest trade deal covering about 30 percent of the world's population.