Grizzly bears in and around Yellowstone National Park should be removed from the endangered species list after 30 years of federal protection, the Department of Interior said Tuesday.

The number of grizzlies in the Yellowstone area has grown at a rate of 4 to 7 percent per year since the bear was listed under the Endangered Species Act in 1975, Interior Secretary Gale Norton said.

Federal wildlife officials estimate that more than 600 grizzly bears now live in the region, which includes parts of Wyoming, Montana and Idaho.

Stripping the bears of protection could eventually clear the way for limited hunting of the massive bears. The three states would assume management responsibilities from federal wildlife officials and have greater flexibility in dealing with the animals.

The bears could be removed from the list as early as 2006, but litigation could delay the move.

Environmental groups are split over the issue. The National Wildlife Federation supports ending the protections, saying it would highlight the success of the endangered species law. The Natural Resources Defense Council, the Sierra Club and other groups say that too many threats still exist for the bears.

Three senators who attended the Interior news conference Tuesday used the event to call for changes in the endangered species law that would enable more animals to be removed from the list. The House passed a bill in September that would lessen the government's role in protecting plant and animal habitat.

Less than 20 species have been removed from the endangered list since the law was signed by President Nixon was signed in 1973.

"This is the exception, not the rule to the Endangered Species Act," Sen. Larry Craig, R-Idaho, said of removing the bears form the list.

Sens. Mike Enzi and Craig Thomas of Wyoming, both Republicans, also called for changes to the law.

Norton said grizzly bear recovery has been a success story because of cooperation between state and federal governments, along with biologists and conservation groups. She said the Bush Administration would like to see the law focused more on recovery efforts than penalizing landowners who find species on their land.

Four other grizzly populations in the lower 48 states will continue to be protected as threatened species under the act. These bears live in the Montana, Wyoming, Idaho and Washington.

Alaskan grizzly bears, which number about 30,000, were never listed under the act.