Nations pushing to create vast ocean sanctuaries off Antarctica that cover an area the size of India hope to overcome objections to their plans at talks this week in Australia.

Two proposals for huge no-fishing havens are on the table at the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) meeting in Hobart from October 23-November 1.

At stake, say environmentalists, are the world's last great ocean wildernesses, with waters that are home to some 16,000 known species, including whales, seals, albatrosses, penguins and unique species of fish.

As the world's fish stocks reel from decades of over-exploitation, trawlers have been venturing ever southward in search of new catches.

"It's time to act," Andrea Kavanagh, director of the Pew Environment Trust's Southern Ocean sanctuaries project, said ahead of the meeting.

"Countries can overcome the false starts of the past year by coming together this month to safeguard these vital areas."

One proposal, floated by Australia, France and the European Union, would protect 1.6 million square kilometres (640,000 sq miles) off East Antarctica, on the frozen continent's Indian Ocean side.

The other, from the United States and New Zealand, is to lock up 1.25 million square kilometres of the Ross Sea, the deep bay on Antarctica's Pacific side.

The combined area of 2.85 million square kilometres is a fraction smaller than India, more than five times larger than France and would fit Britain in 12 times.

If adopted, the sanctuaries would practically double the world's marine reserves overnight.

But to proceed, they need unanimous backing from all members of CCAMLR, a body comprising 24 countries plus the EU, which was set up in 1982 to oversee conservation of marine line in the Southern Ocean.

Russia stymied the plans at a special meeting in Germany in July, concerned the no-fishing areas were too extensive and questioning the legal right of CCAMLR -- pronounced "cam-lar" -- to set up such sanctuaries.

The Russians are believed to have dropped their argument about CCAMLR's legality and there is optimism the sanctuaries will receive support in Hobart.

However, it is understood there have been mixed signals from Russia amid "challenging" negotiations and it remains uncertain how Moscow's delegation will vote.

In a bid to overcome the objections, the backers of the Ross Sea sanctuary have reduced its area by more than 20 percent from the 1.6 million square kilometres they initially put forward.

New Zealand Prime Minister John Key said that revising the plan was probably the only way to get it approved

"We always knew there was going to be resistance from other parties who either have fishing interests there or believe that they would have fishing interests," he said.

Canberra-based think tank the Australian Strategic Policy Institute (ASPI) said the failed meeting in Germany showed "some fishing nations (want) to prioritise fishing access over conservation".

It described the move by the US and New Zealand to preemptively reduce the size of their proposal ahead of the Hobart meeting as a "baffling" negotiating tactic that played into the hands of the sanctuaries' opponents.

"It's difficult to be positive about a good outcome for the Southern Ocean," ASPI concluded in a report released on Monday.

"As one of the last great wildernesses, it deserves special recognition, respect and commitment from those governments that have chosen to manage it."

Backers of the sanctuaries, some of whom have been working on the proposals for eight years, say they will not give up if the Hobart talks end in failure.