New Zealand's plan to make Antarctica's Ross Sea the world's largest marine protected area looks to be hanging by a thread after two countries questioned the legality of the plan.
Members of the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) are examining the proposal, which is backed by the United States.
Russia and the Ukraine, two countries known for opposing the 2.2 million square kilometre protected area, are questioning whether the organisation has the legal power to create the reserves.
Any change in status requires a unanimous decision by the 25 members of the commission.
In what's thought to be the first time ever, the heads of the commission have spoken about the problems being raised in the the negotiations while they're still under way.
CCAMLR chair Terje Lobach said a group of international lawyers would meet during the day to consider Russia and the Ukraine's concerns. However, he said lawyers at the meeting had already said CCAMLR "definitely" had the mandate to proceed.
Mr Lobach said Russia and the Ukraine wanted the size of the Ross Sea deal reduced, an end date for the protection and more fishing areas allowed within the zoned area.
The commission is also considering a proposal backed by the European Union, France and Australia for the waters of East Antarctica, Reuters reports.
Campaigners say establishing the reserves would safeguard the habitat of whales, seals and penguins and more than double the world's protected sea area.
Last November, commission members failed to agree on setting up marine protected areas amid disputes over scientific findings, the duration of the protection period, and a reluctance by some to shut off commercial access to new fishing waters.