The region's trade body says Vanuatu's sudden decision to not sign the PACER-Plus agreement came as an absolute shock.
The regional free trade agreement, which had been negotiated for nearly a decade, would be signed by the region's trade ministers in Tonga this week.
RNZI reports that on Thursday, Vanuatu's government said it would not sign the agreement, joining two of the Pacific's other large economies, Fiji and Papua New Guinea, in refusing to do so.
Steve Siro, from the Office of the Chief Trade Advisor, said the announcement came out of the blue, as it had until a week ago been a big proponent.
"Vanuatu has played a very active role in the negotiations. They have done a lot to keep the negotiations going so that announcement was quite shocking for us," he said.
"In fact, during the recent non-state actors dialogue they also confirmed their firm support for the agreement."
Mr Siro said the withdrawal was disappointing, but the deal would go ahead, and he hoped Vanuatu would one day join.