New Zealand has reiterated calls to protect waters south of the country from overfishing ahead of an anticipated setback next week.
The pressure was not from countries anywhere near Antarctica - but largely from Russia.
A commission had been working for eight years to establish marine protected areas, or MPAs, in Antarctic waters to protect species including the toothfish.
New Zealand's Opposition and Government both called for global recognition of the Antarctic's ecological importance this week. Yet even with powerful international allies backing New Zealand's position, plans for the reserve could be thwarted again.
The next round of talks at the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) will be held in Hobart next week. The commission made decisions by consensus and, without a breakthrough, the reserve could be delayed indefinitely.
Labour's environment spokeswoman Ruth Dyson is concerned about the negotiations after Russia thwarted the conservation plans in the July round of talks.
"It did seem like it was one of those typical brinkmanship international discussions where the opponents were saying: 'If you go too far, we'll pull the plug on everything'," Dyson told the Herald on Sunday. "We just can't have open slather."
After Russia's obstruction, New Zealand and the US made compromises. The original Ross Sea plan would have protected 2.3million sq.km and totally banned commercial fishing in an area of 1.6m sq km. The plan was then slashed 40 per cent after the talks.
Conservation and marine protection network the Antarctic Ocean Alliance said the Hobart talks were critical.
Alliance spokeswoman Blair Palese a number of species were under threat, and some would be wiped out before they were even understood. "It will be one of the last places on the planet... that is yet to be changed by significant human interaction."
Palese said the Alliance was not optimistic the next round would yield meaningful results. She said it seemed Russian distrust of Western countries' proposals underpinned some of the impasse.
The Labour Party said said some commercial fishing firms were lobbying against the reserves, even though sustainably-sourced fish commanded a premium. "If we could move our fishing industry to be regarded and branded as sustainable, that would be good not just for protection of other species," Dyson said, "but actually a real boon for sales of our fish."
This week foreign minister Murray McCully called for global unity to support the reserves, in a a statement co-signed by his peers from Australia, France, the USA and European Union.
"The Ross Sea and East Antarctica regions are widely recognised for their remarkable ecological and scientific importance," the ministers said. "The MPA proposals now before the Commission are based on sound and best available science, will provide a unique laboratory for continuation of marine research, and will have profound and lasting benefits for ocean conservation, including sustainable use of its resources.'