An academic in Fiji says the Forum is caught in a dilemma over whether it accepts plans by Fiji's interim prime minister, Commodore Frank Bainimarama, to attend its leaders' meeting later this year.
Fiji remains a full member of the Forum and its leader, who staged a military takeover of the government, has the right to be present.
But, Forum leaders have previously issued a statement in which good governance is a core principle and which says their vision includes a region which fully observes democratic values and the defense and promotion of human rights.
Dr Steven Ratuva, from the University of the South Pacific, says if the Forum rigidly sticks to its principles, there may be a move to expel Fiji which could eventually break up the Forum.
He says the credibility of the Forum is at question.
"It'll be a big challenge for the Forum - when you have any particular leader of the country has been demonised in different ways, what sort of approach in terms of addressing problems in the Pacific should it take. Should it be engaging? In other words, ok, these are the better guys, lets talk to them, lets try and make sure that we make sense of what he's doing or should you isolate the person."
Dr Steven Ratuva.