The rule was aimed at heading off the possibility that the bear's survival could be cited by opponents of power plants and other facilities that produce carbon dioxide, a leading pollutant blamed for global warming.
The Endangered Species Act requires that a threatened or endangered species must have its habitat protected. Environmentalists say that in the case of the polar bear, the biggest threat comes from pollution
- mainly carbon dioxide from faraway power plants, factories and cars - that is warming the Earth and melting Arctic sea ice.
Salazar agreed that global warming was "the single greatest threat" to the bear's survival, but disagreed that the federal law protecting animals, plants and fish should be used to address climate change.
"The Endangered Species Act is not the appropriate tool for us to deal with what is a global issue, and that is the issue of global warming," said Salazar, echoing much the same view of his Republican predecessor, Dirk Kempthorne, who had declared the polar bear officially threatened and in need of protection under the federal species law.
Kempthorne at the same time issued the "special rule" that limited the scope of the bear's protection to actions within its Arctic home.
The iconic polar bear - some 25,000 of the mammals can be found across the Arctic region from Alaska to Greenland
- has become a symbol of the potential ravages of climate change. Scientists say while the bear population has more than doubled since the 1960s, as many as 15,000 could be lost in the coming decades because of the loss of Arctic sea ice, a key element of its habitat.
Environmentalists and some members of Congress had strongly urged Salazar to rescind the Bush regulation, arguing the bear is not being given the full protection required under the species law.
Others, including most of the business community, argue that making the bear a reason for curtailing greenhouse gases thousands of miles from its home would cause economic chaos.
Reaction to Salazar's decision Friday was sharply divided.
Alaska Gov. Sarah Palin hailed the decision as a "clear victory for Alaska" because it removes the link between bear protection and climate change and should help North Slope oil and gas development. Both of Alaska's senators and its only House member also praised the decision and rejected claims the bear won't be protected.
Sen. James Inhofe of Oklahoma, a global warming skeptic and the ranking Republican on the Senate Environment Committee, applauded Salazar "for making the right call and applying a commonsense approach to the Endangered Species Act" and climate.
But environmentalists and some of their leading advocates in Congress were disappointed.
"The polar bear is threatened, and we need to act," said Sen. Barbara Boxer, D-Calif., who chairs the environment panel, adding that she disagreed with Salazar's decision not to revoke the Bush regulation.