Niue's Premier, Young Vivian, says the country needs to reflect further on the Pacific Islands Air Services Agreement, or PIASA, before signing it.
PIASA aims to create a single aviation market among the island countries in an attempt to boost trade and tourism.
At the Forum summit in Auckland four countries signed, Nauru, Cook Islands, Vanuatu and Tonga.
Six of the 14 island countries need to sign to ratify the agreement.
Fiji has refused, saying it poses a threat to Air Pacific, but Mr Vivian says Niue will eventually sign it.
"On the surface of it all I think it is good but I think there are considerations to think about but as I said at the end of the day, I'm sure we'll sort things out and will sign it"