Pacific Islands Forum leaders sailed to an island retreat off the Auckland coast Thursday to thrash out a communique for the annual summit, with Fiji and climate change set to be key talking points.

The official theme of this year's meeting was supposed to be "turning potential into prosperity" but the presence of UN chief Ban Ki-moon has put the issue of climate change at the top of the agenda.

"I am here to continue sounding the global alarm about climate change," Ban said after addressing the Pacific leaders on Wednesday.

Discontent among some nations over Fiji's expulsion from the forum has also overshadowed the summit's regular discussions on topics such as fisheries and tourism.

But while Fiji will undoubtedly be discussed by the leaders at their Waiheke Island retreat, it unlikely to be mentioned in the communique released later Thursday, as host New Zealand did not put it on the official agenda.

The forum's dominant powers New Zealand and Australia strongly support the Fji ban, imposed after military strongman Voreqe Bainimarama reneged on a promise to hold elections in the wake of a 2006 coup.

Kiribati President Anote Tong ditched the forum's official stance on Fiji Wednesday, describing it as the "bad boy" of the Pacific but arguing it was still part of the regional family and should have a place at the meeting.

"Fiji is part of this family and our task is to continue to bring Fiji back, as you would any child," he said.

The release of the forum communique would normally mark the summit's highlight but New Zealand Prime Minister John Key said that this year the post-forum dialogue, to be held on Friday, would be more important.

This was due to the high-profile guest list at the Auckland gathering, including the UN's Ban, European Commission President Jose Manuel Barroso, French Foreign Minister Alain Juppe and US Deputy Secretary of State Tom Nides.