The five Micronesian member states of the Pacific Island Forum have decided to quit the organisation in response to last week's appointment of a Cook Islander as the new Secretary General.
The presidents of Nauru, the Federated States of Micronesia, Kiribati, Marshall Islands and Palau issued a joint communique, saying they agree to start to initiate the formal process of leaving the Forum.
The leaders collectively expressed disappointment with the appointment process, which overlooked the Micronesian candidate Gerald Zackios.
They say a gentleman's agreement to rotate the Forum's top position among Polynesia, Micronesia and Melanesia was not honoured when a majority of Forum leaders chose Henry Puna of the Cook Islands.
The membership was clearly divided on the matter last year as some Polynesian and Melanesian countries put forward candidates, despite an understanding that it should be Micronesia's turn at the post.
Micronesian leaders first threatened to leave the Forum over the matter months ago
Their departure reduces the Forum to 12 members, all of them in the South Pacific.
New Zealand's foreign minister Nanaia Mahuta attended last week's Forum Leaders meeting where she they were aware the sub-regional group felt strongly about their nominated candidate getting the secretary general's post.
Holding the long-delayed Forum Leaders summit via online video conferencing made for a different kind of meeting to which the regional body is accustomed.
Consensus on the appointment of a new secretary-general to succeed Papua New Guinea's Dame Meg Taylor could not be reached by usual discussion.
But Mahuta said she believed the voting process was geared towards getting consensus on the best person for the role.
According to her, it was not until after the meeting that it became evident Micronesian leaders were intent on leaving the Forum altogether.
"It's regrettable that the Micronesian states have signalled that they intend to pull away.
"I expect that there'll be a high level of conversation amongst leaders to see whether or not we can work to bring everybody into the regional collaboration through the PIF."
Meanwhile, Palau's president Surangel Whipps Jr, who was the first to declare his country was leaving the Forum last week, said the Micronesian leaders' joint decision to leave was a show of unity and solidarity that the rest of the Pacific could learn from.