The Pacific Islands Forum has grown to 18 members after leaders including New Zealand Prime Minister John Key supported French Polynesia and New Caledonia to join the annual meeting.
The two nations had been observer nations until successfully petitioning for full membership at a leaders retreat in Pohnpei in the Federated States of Micronesia on Saturday.
"They have quite developed economies, I think they would actually add a fair bit to the debate and my own view is that forum would be stronger for their admittance," Mr Key said ahead of their bid.
But there was also strong opposition from nations including Fiji, whose Prime Minister Frank Bainimarama also opposes the presence of New Zealand and Australia in the forum.
He is continuing to boycott the forum while the two nations remain involved and is believed to be concerned the inclusion of French Polynesia and New Caledonia will give the French more power over the region.
Fisheries and climate change were also priorities for the regional leaders who attended the annual meeting.
Mr Key is expected to attend a post-forum dialogue on Sunday morning before returning to New Zealand in the evening, winding up a week of meetings with world leaders that began with the East Asia Summit in Laos.