The outgoing chief trade advisor for the Pacific, Dr Edwini Kessie, says he is hopeful that Fiji and Papua New Guinea will eventually join the PACER Plus trade deal.
Fiji complained that it was thrown out of the negotiations but Dr Kessie says that is not so.
They just did not attend the final negotiations, although earlier concerns Fiji had raised had been resolved.
He said with Fiji this week announcing that its intention was not to withdraw he hoped it would accede to the agreement eventually.
Dr Kessie said he hoped that in time PNG would see that the deal had flexibility and be encouraged to sign.
"Obviously if we have an agreement which comprises Fiji and PNG then the whole region will be better off and hopefully, I do hope that those two countries will come on board, with time."
The trade arrangement among Pacific nations is due to be signed in June after negotiations were completed last week.
However a New Zealand Green Party MP Barry Coates said the deal went against the emphasis placed on regionalism by Australia and New Zealand in their aid programmes.
"I think it stands to potentially drive a wedge between the Pacific and I think it is a very unhealthy dynamic to have," he said.
However, Mr Kessie said Mr Coates was wrong to claim there was a lack of access.
He said the issue was the difficulty Pacific Island countries often have in establishing rigorous bio-security systems, but under the deal New Zealand and Australia were committed to help the smaller nations achieve this.
"So the statement that they don't have access to Australia for tropical fruits is not accurate," Dr Kessie said.
"I mean I think it should be said in the context that they cannot meet their applicable bio-security requirements.
And in PACER Plus Australia and New Zealand have undertaken to assist the countries to meet those standards."
Dr Kessie, who has returned to his position at the WTO in Geneva, said he was confident PACER Plus would bring immense benefits to the island nations.
He said if the island leaders didn't also think this they would not have agreed to the deal.