The Micronesian Presidents' Summit (MPS) will release a joint statement concerning Kiribati's shock exit from the Pacific Islands Forum in the coming days.
Federated States of Micronesia president David Panuelo said the four members of the Micronesian bloc, including Marshall Islands, Nauru and Palau, were "saddened" by Kiribati's decision to withdraw from the regional body.
"We believe that the Suva Agreement, when we came last month and met with the forum chair, was a big achievement," Panuelo told RNZ Pacific.
"It was a big surprise for us that Kiribati is not on board."
The Suva Agreement, president Panuelo said, succeeded in achieving the reforms that Micronesian subregion was asking for, and in 18 months would take on the secretary-general position for five years.
"I think that's a very reasonable achievement to also have a subregional office in Micronesia of the Pacific Islands Forum and also the Pacific Ocean Commissioner's office to be in Micronesia," he said.
FMS, the Marshall Islands, Nauru and Palau had agreed to the terms in the Suva Agreement.
Three nations had already signed up to it in June and Nauru was expected to endorse it this week during the leaders meeting.
"Our preference is to humbly invite Kiribati to come on board," he said.
"When one is not on board with the Pacific family we're not quite there yet."
The four MPS leaders, as well as Fijian prime minister and forum chair Frank Bainimarama, had been trying to reach out to the Kiribati government, but they had not had any success.
There had been concerns China had been exerting its political influence behind the scenes prompting Kiribati to isolate itself from the Forum.
But the Chinese foreign ministry denied allegations Beijing had any part in Tarawa's stance, calling it "groundless".
"For years, China and the PIF have sound cooperative relations. I would like to stress that China does not interfere in the internal affairs of Pacific Islands countries (PICs) and hopes to see greater solidarity and closer cooperation among PICs for common development," spokesperson, Wang Wenbin said.
Pacific lead at the Griffith Asia Institute's Pacific Hub, Dr Tess Newton Cain said Kiribati had been on an "isolationist" path for some time.
"We've had not allowing in international media, the media in Kiribati is active but doesn't get a lot of access, doesn't get access to leaders, we've had suspensions of High Court justices," Cain said.
"So, there's been this kind of steady move away from of Pacific Island forum, or just regionalism, generally, and also, I think there's been a retreat from democracy."