Anchorage - Five months after suing to keep polar bears off the U.S. threatened species list, Alaska's government said Wednesday it plans to issue a similar challenge to block federal protections for a struggling population of beluga whales in Cook Inlet, a mature oil-producing basin.

Former vice presidential hopeful Gov. Sarah Palin said the energy-rich state believes the Endangered Species Act protections for belugas announced in October by the National Oceanic and Atmospheric Administration are unwarranted.

"The State of Alaska has worked cooperatively with the federal government to protect and conserve beluga whales in Cook Inlet," the Republican governor said in a news release announcing that a 60-day notice of intent to sue had been sent to NOAA. "This listing decision didn't take those efforts into account as required by law."

Beluga whales swimming in Cook Inlet, a glacier-fed saltwater channel running from Anchorage to the Gulf of Alaska, numbered as high as 1,300 three decades ago, but has dropped to about 375 since then, according to NOAA.

Alaska's announcement it would challenge the endangered listing drew ire from environmental groups.

"Once again Governor Palin has demonstrated either a complete lack of understanding or lack of concern over the plight of endangered species," Brendan Cummings, oceans program director for the Center for Biological Diversity, said in a statement Wednesday.

Federal scientists believe overhunting by the area's Alaska Native population caused the decline in the beluga population.

But Alaska officials say the whales are recovering due to some recent controls on hunting, said Doug Vincent-Lang, an official at the Alaska Department of Fish and Game.

"The main threat has been addressed," he said.

The state and several municipal governments and business groups argue that an endangered listing will hamper business in Alaska's most densely populated region.

Among the affected activities would be offshore oil and gas operations in the mature Cook Inlet basin, they argue. Major Cook Inlet oil and gas operators are Unocal, Marathon Oil, ConocoPhillips and Chevron.

The decision to pursue a lawsuit challenging the beluga listing follows an August lawsuit filed by the Palin administration that seeks to overturn the threatened listing for the polar bear.

The state of Alaska is arguing that listing polar bears as a threatened species will hurt Alaskan oil and gas exploration, fisheries and tourism.