A US federal judge is considering temporarily suspending the capture of wild horses in the state of Nevada, where advocates say the federal government is “needlessly and recklessly” killing free-roaming mustangs in violation of US laws.

District judge Miranda Du said she expects to rule by Monday on the advocates’ request for an emergency court order pending another hearing next week to learn more about the potential danger of round-ups near the Utah state line.

The US bureau of land management insists it must gather the mustangs before the end of February – one of several such events scheduled on an expedited basis across the American west due to severe drought.

Maggie Smith, a US justice department lawyer, said a delay of even two or three days would prevent the agency from completing the removals before the end of the year.

Wild horses
Mustangs, recently captured on federal rangeland, roam a corral at a facility north of Reno (AP)

The bureau is prohibited from using helicopters to drive the herds into temporary corrals from March 1 to June 1, when mares are typically pregnant and give birth.

After that, the summer heat adds stress on the animals and in the autumn, contractor availability becomes a problem, Ms Smith said.

The horse advocates say the agency is squeezing the round-up of 2,030 horses in Nevada into a month under an illegal environmental assessment of a series of gatherings over 10 years.

Of the 1,048 horses gathered as of Wednesday, the bureau says 11 have died.

Advocates say the low-flying helicopters used combined with “unsafe muddy conditions on the ground in mid-January create a purely artificial hazard that is deadly to these wild horses, a congressional protected, public natural resource”.

“This particular herd is foaling now and pregnant now,” Jessica Blome, their lawyer, told Judge Du.

“If they had followed the proper process and monitored the herd, they would know that.”