U.S. wildlife managers failed to adopt a recovery plan for the endangered Mexican gray wolf that would protect against illegal killings and the consequences of inbreeding, according to a lawsuit filed Tuesday by environmentalists.

A coalition of environmental groups filed the complaint in federal court in Arizona, marking the latest challenge in a decades-long battle over efforts to re-establish the predator in its historic range in the American Southwest and northern Mexico.

The lawsuit alleges the plan adopted by the U.S. Fish and Wildlife Service set inadequate population goals for the wolves, cut off access to vital habitat in other parts of the West and failed to respond to mounting genetic threats.

In approving the recovery plan, federal authorities acknowledged that majority of documented mortalities in the United States are human-caused

"Mexican wolves urgently need more room to roam, protection from killing and more releases of wolves into the wild to improve genetic diversity, but the Mexican wolf recovery plan provides none of these things," said Earthjustice attorney Elizabeth Forsyth, who is representing the groups. "The wolves will face an ongoing threat to their survival unless major changes are made."

Federal officials did not immediately respond Tuesday to emailed messages seeking comment about the lawsuit but have previously defended the plan, which was adopted in November after decades of legal wrangling and political battles.

The majority of documented Mexican gray wolf deaths in the U.S. are human-caused, and officials said in the recovery plan that reducing mortalities from illegal shootings and vehicle collisions may "provide our best opportunity to improve population performance and speed the time to recovery."

Investigations of illegal shootings over the years have not produced suspects, but federal authorities offer a $10,000 reward for information leading to the apprehension of individuals responsible for illegal Mexican wolf killings. Other groups have donated more money, meaning tipsters could get as much as $58,000 depending on the information they provide.

Under the plan, management of the wolves would eventually revert to state wildlife agencies in New Mexico and Arizona but not until the population averages 320 wolves over an eight-year period. In each of the last three years, the population would have to exceed the average to ensure the species doesn't backslide.

Officials with the wolf recovery team are currently surveying the population to get an updated count. Last year, the survey found at least 113 wolves in the wild in mountainous areas along the Arizona-New Mexico border.

Environmentalists have pressed for years for more captive wolves to be released into the wild. Ranchers and elected officials in rural communities argue against doing so, citing wolf attacks on livestock.

According to the lawsuit, the Mexican gray wolf is one of the most genetically and ecologically distinct lineages of wolves in the Western Hemisphere.

After extermination campaigns on both sides of the U.S.-Mexico border decades ago, the last known wild Mexican gray wolf in the United States was killed in 1970, officials have said.

Seven wolves formed the stock for a captive breeding program. Five had been captured in Mexico between 1977 and 1980 and the other two were already in captivity.

The reintroduction effort began in 1998 with the release of 11 captive-bred wolves.