ATLANTA, Georgia (CNN) -- Polar bears will now be listed as "threatened" under the Endangered Species Act.
Scientists predict that two-thirds of the world's polar bears will disappear in the next 50 years.
But in announcing the listing, Secretary of the Interior Dirk Kempthorne said the decision should not be "misused" to regulate global climate change.
"Listing the polar bear as threatened can reduce avoidable losses of polar bears. But it should not open the door to use of the Endangered Species Act to regulate greenhouse gas emissions from automobiles, power plants, and other sources," said Kempthorne.
"That would be a wholly inappropriate use of the ESA law. The ESA is not the right tool to set U.S. climate policy." Watch Kempthorne explain the decision »
While there are an estimated 20,000 to 25,000 polar bears now in the Arctic, scientists from the U.S. Geological Survey predict two thirds of the world's polar bears will disappear in the next 50 years because of a decline in Arctic sea ice. Learn more about polar bears and their habitat »
Controversy over the status of the polar bear is tied to the fact that this is the first time a species has been considered for listing specifically because its habitat is threatened by global warming.
The announcement is getting mixed reviews.
Some environmental groups are wary of some of the climate change caveats to the decision, saying it weakens protection for the animals.
"This decision is a watershed event because it has forced the Bush administration to acknowledge global warming's brutal impacts," said Kassie Siegel, climate program director at the Center for Biological Diversity.
"It's not too late to save the polar bear, and we'll keep fighting to ensure that the polar bear gets the help it needs through the full protections of the Endangered Species Act. The administration's attempts to reduce protection to the polar bear from greenhouse gas emissions are illegal and won't hold up in court," said Siegel.
But other animal protection organizations praised the decision.
"Today's decision is a tremendous victory for one of the world's most iconic and charismatic animals," said Carter Roberts, president and CEO of World Wildlife Fund US on the group's Web site. "The other big winner today is sound science, which has clearly trumped politics, providing polar bears a new lease on life."
Some members of Congress are less than thrilled with the decision.
Rep. Edward J. Markey, D-Massachusetts, is Chairman of the Select Committee on Energy Independence and Global Warming.
"After years of delay, the Bush administration was forced to face the reality that global warming has endangered the polar bear and that the polar bear needs to be placed on the Endangered Species Act," said Markey in a statement to CNN. "But the administration has also simultaneously announced a rule aimed at allowing oil and gas drilling in the Arctic to continue unchecked even in the face of the polar bear's threatened extinction. Essentially, the administration is giving a gift to Big Oil, and short shrift to the polar bear."
The Center for Biological Diversity was one of three environmental groups, including Greenpeace and the Natural Resources Defense Council, that sued the federal government to force a decision on the status of the polar bears.
The Bush administration was supposed to make a decision on the status of the polar bear by January 9 of this year. Early this month, U.S. District Judge Claudia Wilken of the Northern District of California agreed with the conservation groups, ordering that the Department of the Interior announce a decision by May 15.
Some environmentalists say the delay of a decision, was made to make it easier for oil companies to finalize $2.7 billion in offshore oil leases in the Chukchi Sea. That area between Alaska and Siberia is home to about 20 percent of the planet's polar bears.
"Had the polar bear been listed prior to January 9 as the law required, that lease sale could not have moved forward without some substantial additional review of the impacts to polar bears," said Siegel.
At a Congressional hearing in January, the head of the Fish and Wildlife Service said those leases do not pose a risk to the bears.
"We don't have any substantial records that the oil and gas exploration have created an issue for the polar bear," said Dale Hall, director of Fish and Wildlife.
USGS scientist Steve Amstrup, who has studied polar bears for nearly 30 years, explained why the sea ice can mean life or death for polar bears. Amstrup spoke to CNN in March.
"A lot of people don't understand how polar bears live. They are not terrestrial animals. They spend very little time on land. They spend most of their time on sea ice, this cap of ice that is floating around on the surface of the Arctic Ocean. It is on that surface of the ice that they have adapted ways of catching seals that are their principal prey.
"These seals are kind of like giant 'fat pills' that have allowed polar bears to become the largest of the bears and to expand across the range of the sea ice. As that sea ice declines, you can think of it as a decline in the carrying capacity of polar bears, just as if you took a field that supported a certain number of cattle, for example, and plowed up half the field and there was no longer grass there, you've lost the carrying capacity for half the animals that live out there," said Amstrup.
Scientists from the World Wildlife Fund said before Kempthorne's announcement that a positive decision on the bear's status could mean the United States could regain a leadership role in global species conservation.
"The polar bear is a compelling symbol. What is happening to the polar bear is happening to the Arctic. And it's happening more rapidly and more severely than anywhere in the world. It is a signal we are in deep trouble, that we need to take action on climate change", said Margaret Williams, managing director of the Kamchatka-Bering Sea Ecoregion for the World Wildlife Fund U.S.