Ministers from 15 Asia-Pacific countries say they aim to implement a free-trade pact by early January. The Regional Comprehensive Economic Partnership, or RCEP will cover about 30 percent of the world's population and GDP after it takes effect.
Japan's economy minister Kajiyama Hiroshi and his counterparts reached the agreement in a teleconference earlier this week.
It is the first time that all participating nations have agreed on the specific timing for the partnership's inception.
The deal was signed last November by Japan, China, South Korea, Australia, and New Zealand. The other 10 signatories are the members of the Association of Southeast Asian Nations.
Japan, China and Singapore have already completed domestic procedures to approve the RCEP. It will take effect 60 days after ratification is completed in six of the 10 ASEAN members and three of the five other nations.