The deal was signed in June, but three of the region's largest countries - Papua New Guinea, Fiji and Vanuatu - refused to join, saying it would harm their economies and was imbalanced towards Australia and New Zealand.
The negotiator, Tessa Te Mata, said PACER Plus was about building on existing regional trade agreements and adding to the dynamism, economic integration and trade in the region.
She said the countries that refused to join needed to work out how PACER Plus would work for them and what they wanted from it.