An economic watchdog, the Pacific Network on Globalisation, is warning that regional trade deal Pacer Plus will place a burden on Pacific Island nations.
The deal, which involves 11 Pacific countries, including Australia and New Zealand, is expected to come into force later this year.
So far three have ratified and two more have signalled they plan to do so, including the Cook Islands.
Two of the deal's key aspects for island countries are a commitment to extra development aid and labour mobility into Australia and New Zealand.
But the network's Adam Wolfenden said the deal was "unbalanced" as those aspects were non-binding and would not result in anything concrete for the island nations.
"So the annual meeting that is essentially the only outcome on labour mobility, and the development assistance component, which is [coming] from existing aid budgets, present a zero sum game for the Pacific.
"They are not really getting anything new under these arrangements."