Polar bears could die out by 2050, the Word Wildlife Federation (WWF) environment organisation warned following a new US study.
The report by the US Geological Survey predicts that climate change and melting sea ice could drive two-thirds of them to extinction by mid-century, which WWF said on Tuesday was "almost certainly an underestimate".
"We now have official confirmation that the largest living land predator is going to go extinct in our lifetime," said Neil Hamilton head of the WWF Arctic programme, speaking in Geneva.
The US study said the survival of polar bears was dependent on sea ice, which they use as a platform to hunt seals, their primary food.
The report forecast a 42 per cent loss of sea ice across the Arctic during summer in the coming 50 years on top of the reduction in habitat already recorded during the past 20 years.
The impact was expected to decimate the polar bear population estimated between 20,000 and 25,000 today.
The WWF insists the reality is even worse than the study and suggests that sea-ice loss was consistently underestimated by current computer models.
"Politicians are still fiddling at the edges while the Arctic succumbs to global warming; but in the meantime, they are sending one of the world's greatest species on its way to extinction," added Hamilton.
The US government was to decide in January whether to list the animal as a threatened species on the strength of the report.