A group of environmental organisations this week announced it is suing the Bush administration for failing to decide whether the polar bear is an endangered species or not – a delay they claim is intended to ease the sale of controversial oil drilling rights in the bears' habitat.

Greenpeace has teamed up with the Centre for Biological Diversity (CBD) and the Natural Resources Defence Council (NRDC) to pursue the suit, after the administration missed a legal deadline to decide whether it would classify the species as endangered or not.

The groups have also linked the administration's inactivity to the recent sale of oil drilling rights in the bears' native habitat.

The groups issued a scientific petition to have the polar bears listed under the Endangered Species Act, and sued the administration in December 2005 for failing to respond. Two months later, the US Fish and Wildlife Service said that the protection of the species "may be warranted" and initiated a review, says the CBD. The results of that decision are now more than two months overdue.

The lawsuit comes at the same time as legislation was introduced into Congress to make a decision on the status of polar bears before drilling rights in the region could be sold to oil companies in the region.

However, the Minerals Management Service, which like the Fish and Wildlife Service is part of the US government's Interior Department agency, proceeded with an oil lease sale in the Chuckchi Sea in Alaska in February.

"They offered 30m acres of prime polar bear habitat in the Chuckchi sea to oil companies," said Kassie Siegel, executive director of the CBD. "There was no urgency to hold the lease sale. Those fossil fuels won't be available for use for a decade. The only urgency to it was that had they listed the polar bear before 9 January as they were required to under law, they couldn't have gone ahead with the lease sale at that time, because they would have needed to conduct substantial additional environmental review on the impact to polar bears."

Both the UN and the US Geological Survey have joined many environmental groups in now considering the polar bear an endangered species because of global warming, which is reducing the amount of ice on which it has to live.