Wild horses being mustered by helicopter in Nevada.
The state's Bureau of Land Management intends targeting three herds within the next 30 to 60 days.
The mustered horses will be taken into care and eventually offered for adoption.
The bureau says the situation has resulted from 10 consecutive years of drought, overpopulations of wild horses in some herd areas and poor forage conditions.
It will receive extra funding for the emergency musters of nearly 1700 horses from three areas - the Nevada Wild Horse Range north of Las Vegas on the Nevada Test and Training Range; the North Stillwater Herd Management Area south of Winnemucca; and the Fox and Lake Herd Management Area south of Gerlach.
Monitoring of the herd areas reveals competition from too many horses for dwindling water supplies and extremely poor forage conditions.
"Without an emergency gather, many of these horses could perish on the range," a spokesperson said.
"BLM expects to start gathering the Nevada Wild Horse Range and the North Stillwater Herd management Area within the next two weeks."
Gathered horses will be taken to the bureau's holding facilities, in Ridgecrest, California, and Fallon or Palomino Valley, in Nevada. They will be offered for public adoption about 45 days later.
Under the 1971 Wild Free-Roaming Horses and Burros Act, the bureau is required to manage horses and burros only in those areas where they were found in 1971.
Through land-use planning, it evaluates each herd area to determine if it has adequate food, water, cover and space to sustain healthy and diverse wild horse and burro populations over the long term.
Nearly half of the wild horses and burros in the US live on Nevada rangelands managed by the bureau. These Nevada horses move with the seasons within 102 herd management areas comprising nearly 16 million acres of public land.
Having herd populations at appropriate management levels is key to managing the rangeland resources.