The prime minister of Tonga says he hopes the other island nations in the Pacific Islands Forum can encourage Fiji to return to the fold.
Fiji's leader, Frank Bainimarama, says he will not take up an invitation to attend the agency's annual leaders' talkfest in Papua New Guinea in September.
Mr Bainimarama has refused to re-take Fiji's seat as long as New Zealand and Australia remain members, or unless the membership is opened up to other donor countries.
Tonga's Akilisi Pohiva says if the small nations stick together they could eventually convince Fiji to stay but he says New Zealand and Australia must remain as members.
"Tonga respects the independence of every state in the South Pacific. Maybe Fiji has good reason to remain isolated. I still want to see New Zealand and Australia hang on to the Pacific Forum."
Akilisi Pohiva says any issues around membership should be discussed at the Forum summit.