Federal wildlife managers on Friday declined to upgrade protections for a population of grizzly bears in the remote reaches of Idaho and northwest Montana that numbers fewer than 50, and which conservationists say are going extinct.

The U.S. Fish and Wildlife Service said the outsized, hump-shouldered bears that roam the Cabinet Mountains and Yaak River drainage in the Northern Rockies are likely to reach a recovery goal of 100 without changing their status to endangered from threatened under the federal Endangered Species Act.

The finding comes after the Montana-based Alliance for the Wild Rockies sued in April to force federal wildlife managers to tighten restrictions on logging, road construction and other human activity on public land that make up the bears' habitat.

The Fish and Wildlife Service had for years determined that classifying the bears as endangered was warranted, but other imperiled animals took precedence.

The agency last year published a report showing that the grizzlies that range across the so-called Cabinet-Yaak ecosystem were declining at an annual rate of about 0.8 percent and that the percentage of bears unlawfully or accidentally killed each year by humans tripled by 1999-2012 compared with 1982-1998.

Yet, in a decision published in Friday's Federal Register, the Fish and Wildlife Service said the population's status has been improving for the past several years.

"The population trend has now changed from declining to stable," the agency wrote.

Mike Garrity, head of Alliance for the Wild Rockies, contended the population is doomed to extinction.

"The federal government has written off these grizzlies but we won't let them disappear on our watch," said Garrity, who on Friday notified the Obama administration that the group would sue over violations of the Endangered Species Act.

Also on Friday, the administration said a separate population of grizzlies on Idaho's border with Canada likewise did not warrant additional safeguards, saying the population in the Selkirk Mountains was nearing recovery goals of 90 bears.

Grizzlies in 1975 were listed as threatened in the lower 48 states after hunting, trapping and poisoning pushed them near extinction.

A government panel that oversees the roughly 600 grizzlies in and around Yellowstone National Park has said that the population has recovered and should be stripped of federal protections, opening the way for hunting.