A two-year effort to ban wolf hunts in the Rocky Mountain states has ended, with the federal government lifting its protection for the animals.

The interior secretary, Ken Salazar, said wolf populations in the Rocky Mountains had rebounded to sustainable levels.

Federal protection for wolves is also on the way out in Minnesota, Michigan and Wisconsin, he said.

"Like other iconic species such as the whooping crane, the brown pelican and the bald eagle, the recovery of the grey wolf is another success story of the Endangered Species Act," Salazar said. "From a biological perspective, they have now recovered."

Environmental organisations said the move was premature.

Montana and Idaho were already making plans to open hunting in the autumn. The federal government did not end protections in Wyoming, where authorities have been insisting on shoot-on-sight rules for wolves.

All three states had been pushing hard to remove federal government protections for wolves, arguing that populations had more than recovered and were threatening ranchers.

In 2009, federal wildlife officials agreed, but environmental organisations were able to block the state governments for two years in the courts.

The states got their chance last month when the White House and Congress agreed to de-fund or block a number of environmental measures as the price for getting a budget passed.

It was the first time Congress had intervened to remove federal protections for a plant or animal. Environmental organisations are afraid that the two states will now move to drastically reduce populations, in the name of protecting livestock.

Montana, in a preliminary hunt plan, is proposing to allow the killing of 220 wolves this autumn, three times the number killed two years ago, and about 40% of the existing population.