BILLINGS, Mont. (AP)—U.S. wildlife officials plan to lift protections for gray wolves across the Lower 48 states, re-igniting the legal battle over a predator that’s run into conflicts with farmers and ranchers after rebounding in some regions.

Acting Interior Secretary David Bernhardt announced the proposal during a Wednesday speech at the North American Wildlife and Natural Resources Conference in Denver, a week-long conservation forum for researchers, government officials and others, U.S. Fish and Wildlife Spokesman Gavin Shire said.

The decision was based on gray wolves successfully recovering from widespread extermination last century, Shire said.

Wildlife conservation groups reacted with outrage and promised to challenge in court any attempt to lift protections. Agriculture groups, sportsmen and lawmakers from Western states are likely to support the administration’s proposal.

Long despised by farmers and ranchers, wolves were shot, trapped and poisoned out of existence in most of the U.S. by the mid-20th century.

They received endangered species protections in 1975, when there were about 1,000 left, only in northern Minnesota. Now more than 5,000 of the animals live in the contiguous U.S.

Most are in the Western Great Lakes and Northern Rockies regions. Protections for the Northern Rockies population were lifted in 2011 and hundreds of wolves are killed annually by hunters in Wyoming, Idaho and Montana.

State officials and government biologists have said wolves continue to thrive despite pressure from hunting. The animals are prolific breeders and can adapt to a variety of habitats.

But wildlife advocates have fought to keep federal protections kept in place until wolves repopulate more of their historic range that stretched across most of North America.

Since being reintroduced in Yellowstone National park and central Idaho in the mid-1990s, the Northern Rockies population has expanded to parts of Oregon, Washington and California.

The Fish and Wildlife Service has argued for years that gray wolves have recovered in the lower 48 states, despite environmentalists who contend they occupy about 15 percent of the territory they once roamed. Agency officials insist that recovery of wolves everywhere is not required for the species no longer to be in danger of extinction.

The government first proposed revoking the wolf’s protected status across the Lower 48 states in 2013, but backed off after federal courts struck down its plan for “delisting” the species in the western Great Lakes region states of Michigan, Minnesota and Wisconsin.

“Recovery of the gray wolf under the Endangered Species Act is one of our nation’s great conservation successes, with the wolf joining other cherished species, such as the bald eagle, that have been brought back from the brink,” Shire said.

Jamie Clark, a former director of the Fish and Wildlife Service now with the Defenders of Wildlife group, said endangered species protections were needed to prevent “an all-out war on wolves” in states that would allow hunting.

“We don’t have any confidence that wolves will be managed like other wildlife,” she said. “We’re going to fight this in any way possible.”