The Bush administration yesterday made one of its most significant concessions to date on the dangers of global warming, proposing protection for the polar bear, whose habitat is threatened by the melting Arctic sea ice.

The recommendation by the interior secretary, Dick Kempthorne, that the bears be added to the list of threatened species, marks a reversal by the administration from its reluctance to acknowledge the consequences of climate change.

It would bar US government agencies from any activity that would jeopardise polar bears or their hunting grounds, and could potentially require the administration to compel US industries to curb their carbon dioxide output.

There are an estimated 22,000-25,000 polar bears worldwide with populations in the US, Canada, Greenland, Norway and Russia. However, according to a report last month by the World Conservation Union, five of these populations are in decline.

Scientists have observed that the bears are behaving differently to only a decade or so ago. Some have been found looking for food closer to human communities, others are changing diets and there have been three reported incidents of cannibalism.

Polar bear populations in Canada's western Hudson Bay and the southern Beaufort Sea, which is shared between the US and Canada, have declined by 22% and 17% respectively over the past 20 years.