The announcement comes at a time when the bureau has been under increasing pressure from Western ranchers to step up removal of horses they say threaten livestock and wildlife on drought-ravaged rangelands.
The bureau estimates 40,600 of the animals the vast majority of them horses roam free on public rangelands in 10 Western states. The population exceeds by some 14,000 the number the agency has determined can exist in balance with other rangeland resources and uses.
Bureau officials said aggravating the situation is severe drought that has resulted in reduced forage for the animals. The agency also faces limits on the number of horses and burros it can remove because holding facilities are at capacity. Some 49,000 of the animals are being held in government-funded short- and long-term facilities.
Removal of fewer mustangs from the range "will exacerbate the difficult challenges we face in nearly every aspect of the wild horse program right now," BLM officials said in a statement.
But the bureau's actions contradict recommendations of an independent panel of the National Academy of Sciences released last year, said Deniz Bolbol, spokeswoman for the American Wild Horse Preservation Campaign.
In a report, the panel said the bureau should invest in widespread fertility control of the mustangs instead of spending millions to house them. It concluded the bureau's removal of nearly 100,000 horses from the Western range over the past decade is probably having the opposite effect of its intention to ease ecological damage and reduce overpopulated herds.
"The BLM already warehouses more wild horses in holding facilities than remain free in the wild," Bolbol said in a statement. "The agency's plan to remove thousands more mustangs and burros from the range makes no ecological, scientific or fiscal sense."
Horse defenders also dispute the bureau's position that mustangs are overpopulating the West. They say the vast majority of forage on the range is being allocated to privately owned livestock, and public rangelands are being overrun by livestock instead.
"The hyper-focus on mustang numbers is a concerted effort to scapegoat wild horses and distract attention away from the massive level of livestock grazing that is occurring on our public lands," said Suzanne Roy, director of the AWHPC.