Wolf supporters moved Wednesday to force the federal government to develop a broader recovery plan for wolves across more of the U.S. even as the Trump administration and other groups are trying to remove federal protections for the big predators.

The Center for Biological Diversity on Wednesday filed a notice of intent to sue the U.S. Fish and Wildlife Service for violating the Endangered Species Act by never developing a comprehensive recovery plan for gray wolves nationwide.

The notice is a legal heads-up that a lawsuit is coming in 60 days.

According to federal court rulings, under the Endangered Species Act, wolves must remain protected until the Fish and Wildlife Service implements such a plan.

"With federal protections, gray wolves have made tremendous progress, but they're not yet recovered nationwide," said Collette Adkins, Minnesota-based attorney for the Center for Biological Diversity. "If successful, our lawsuit would require the federal government to foster wolf populations in suitable areas across the country rather than rush to prematurely remove safeguards."

But the federal agency in June went the opposite direction, saying it would yet again file a formal plan later in 2018 to remove wolves from federal protections entirely because they have recovered in enough places to ensure their survival as a species - including Minnesota, Wisconsin and Michigan.

The agency has tried multiple times - through the Clinton, Bush and Obama administrations - to delist wolves in Minnesota, Wisconsin and Michigan, saying the big predators have fully recovered here after brushing with extinction in the 1960s and '70s.

The most recent of those efforts, in 2012, allowed state agencies to hold wolf trapping and hunting seasons for three years, until late 2014 when a federal judge ruled that the agency had erred in taking wolves off the endangered list too soon.

That December 2014 decision was upheld in 2017 by a federal appeals court decision that continues to protect wolves across the region today.

Several bills have been introduced in Congress, one as recently as last week, to end federal protections for wolves. So far, none of those has passed both the House and Senate. Livestock and some hunting groups say wolf numbers are already too high - especially in Minnesota, Wisconsin and parts of the Rockies - and that wolf numbers need to be culled by hunting and trapping.

Wolf supporters say they want a federal plan to allow wolves to roam beyond where they are now into more areas they occupied before European settlement and before widespread wolf killing nearly forced the animal's extinction. They say a new recovery plan also would enable wolves to establish viable populations in areas where small populations are still recovering, such as California, Oregon and Washington.

"The Fish and Wildlife Service needs to chart a path toward truly recovering wolves... in suitable habitats across the country,'' Adkins said.

The Minnesota Department of Natural Resources estimated last year that the state has about 2,856 wolves. The Wisconsin DNR earlier this month said its annual winter survey showed as many as 944 wolves in the state, down about 2 percent from the estimated 956 last year, the state's modern-day record. Michigan's Upper Peninsula has more than 500 wolves.

Wolf supporters Monday criticized the DNR for not using better science and technology to pinpoint the wolf population.

"The current method of estimating wolves is not only inaccurate, it tells us very little about how our wolves are doing and their future potential to exist in their changing habitat,'' said Maureen Hackett, president of Howling for Wolves, noting that "26 of the 54 wolves collared for this population estimate have gone missing or are dead."