A proposal by the United States and New Zealand to create a huge ocean reserve in Antarctic waters has been sharply reduced in scale after opposition from China, Russia and other nations with large fishing industries.
Environmentalists warned that the ambitious project was being badly undermined.
The Ross Sea marine protected area that the two governments proposed last year was to have set aside about 2.2 million square kilometres of the Southern Ocean where commercial fishing would be sharply limited.
The area's relatively pristine ecosystem is crucial to the survival of thousands of species, including whales, seals and penguins, as well as the small fish and crustaceans on which they depend.
On Friday, however, New Zealand announced that the overall size of the proposed reserve was being reduced by 40 per cent to gain the support of member nations on the Commission for the Conservation of Antarctic Marine Living Resources, the international body that sets conservation policy for the Southern Ocean, of which the Ross Sea is a part.
Commission delegates are scheduled to meet next month in Hobart, Tasmania, to consider the proposal.
It was clear in July that the US-New Zealand proposal was on shaky ground after a commission meeting in Bremerhaven, Germany, broke up without reaching any agreement.
Supporters of the proposal expected delegates there to work on ironing out details and were stunned when Russia and Ukraine raised legal and procedural questions that halted the discussion, and questioned the commission's authority to create such reserves.
Norway, China and Japan led other fishing nations in calling for smaller reserves, and for "sunset clause" provisions that would allow for the possibility of eventual commercial exploitation of the areas.
Most of the fishing activity in the Ross Sea now is directed at the slow-maturing Patagonian toothfish, often marketed as Chilean sea bass. But there is growing interest in harvesting krill, the tiny creatures that are a pillar of the Southern Ocean ecosystem, and many fishing nations do not want to seal off any future possibilities as fish stocks elsewhere in the world are depleted.
Non-governmental organisations have accused Washington and Wellington of caving in without a fight.
The Antarctic Ocean Alliance, a coalition of 30 environmental groups, said that the scaled-down version of the proposal was a "tactical mistake and a significant retreat for Southern Ocean protection".