Samoa's prime minister Tuilaepa Sa'ilele Malielegaoi says the Pacific Islands Forum must address whether its headquarters should remain in the Fiji capital, Suva.
In a statement to the state- owned newspaper, The Savali, Tuilaepa says the Forum would continue to move from strength to strength.
He says if Frank Bainimarama is serious with his plan not to attend the Papua New Guinea summit he must formally notify the chair, the president of Palau, through the secretary general, Dame Meg Taylor.
Dame Meg said earlier this month that her attempts to speak with Mr Bainimarama since her arrival four months ago have failed.
Tuilaepa says the leaders must decide at the September meeting whether to move the Forum Secretariat out of Fiji.