Vanuatu's opposition leader Ralph Regenvanu has urged countries who support Pacific regionalism to take action to help stop Micronesia leaving the Pacific Forum.
His call comes after Nauru, Kiribati, Marshall Islands, Palau and the Federated States of Micronesia decided to initiate the formal process of withdrawing from the Forum.
The leaders of these countries said that by overlooking Micronesia's candidate in the appointment of a new Forum secretary general, South Pacific countries dishonoured a "gentleman's agreement" to rotate the post evenly among sub-regions.
Regenvanu, an experienced leader in the Foreign Affairs portfolio, said he understood Micronesia's frustration.
"It's just very sad and unfortunate that these kind of agreements that have held together the Pacific for so long, the unspoken Pacific Way of respect, reciprocity, the values that we hold in our Pacific cultures, that they're starting not to be honoured."
Regenvanu said the Micronesians had made their nomination well in advance, as well as their concern that the post be rotated fairly, and should have got the post.
"I'm not surprised at the move of the Micronesians to wish to withdraw from the Forum," he said.
"I think it's up to the countries that support Pacific regionalism to do something to try and stop them leaving, address the issue that's arisen to cause this division."
Regenvanu urged Vanuatu's Prime Minister Bob Loughman to offer to play a role as mediator in the current fallout among Pacific Islands Forum members.
Meanwhile, Australia's Foreign Minister Marise Payne appealed to Micronesian countries to remain engaged with the Pacific Forum
She said she appreciated the disappointment that governments across Micronesia had with the Forum Secretary-General outcome.
But she said she hoped that they decide to remain engaged with the Forum, adding that Australia's relationships with those nations remain close.