Kiribati has confirmed it is leaving the Pacific Islands Forum.
The Ministry of Foreign Affairs said it made the decision official last month.
Kiribati and four other Micronesian countries announced their intention to withdraw earlier this year when Micronesia's candidate for Forum secretary-general was overlooked.
The five governments said this was a breach of a gentlemen's agreement on sub-regional rotation of the Forum's top job.
The new secretary-general Henry Puna appealed to Micronesia to stay with the Forum.
But Kiribati said there is no value of remaining if the agreement is not honoured.
Leaders of countries including Papua New Guinea's James Marape and other leaders have appealed to the Micronesians to stay with the Forum, saying the whole region is stronger when standing together.
PNG was one of the member countries that voted for Micronesia's candidate, the Marshall Islands diplomat Gerald Zackios, when the vote was held near the start of the year.
But Puna's controversial selection remains a red line for the five Micronesia countries.
Kiribati said it was "was gravely concerned by the lack of transparency on the changes and delays made on the deadline for nominations for the post of Secretary General including the dates decided for the Special Forum Leaders Retreat and selection of the new Secretary General."