Sheryl Crow and other wild-horse advocates on Thursday called on President Barack Obama and Senate Majority Leader Harry Reid to block a major roundup of mustangs set to begin Monday in Nevada.

The request came a day after a federal judge denied a request to block the government gather in the Calico Mountains Complex, saying opponents failed to demonstrate that removal of the horses would violate federal law.

In urging Obama and Reid to intervene, Crow and other horse defenders said U.S. District Judge Paul Friedman did side with them in one aspect of his ruling.

The judge said federal officials likely were violating federal law by stockpiling tens of thousands of horses in long-term holding facilities in the Midwest. Friedman invited both sides to offer more legal arguments on the issue but said Congress ultimately may have to get involved.

"I'm asking President Obama and Senator Reid to stop the Calico roundup of the American wild mustangs in Nevada now until Congress decides how to manage our living legends of the West," Crow said in a statement released by the Colorado-based horse advocacy group Cloud Foundation. The Grammy-winning singer has campaigned for both Obama and Reid.

Reid spokesman Jon Summers said the Nevada senator believes it's the U.S. Bureau of Land Management's responsibility to ensure the viability of wild horse herds and to protect rangelands and wildlife.

"Sen. Reid has long been critical of the BLM's wild horse and burro program, as they regularly fall short on their obligations," Summers said. "In this situation, the BLM has failed to properly manage these herds for many years, requiring the large (Calico) gather."

Kendra Barkoff, a spokeswoman for Interior Secretary Ken Salazar, said the roundup will ensure high quality habitat for the wild horses and burros while protecting public rangeland from overuse.

"Secretary Salazar believes that this is once again another clarion call to develop and implement a long-term solution to the challenges we face concerning wild horses and burros on our public lands," Barkoff said.

BLM officials have said they are moving forward with the plan to round up about 2,500 wild horses in northern Nevada, and place them for adoption or send them to long-term holding facilities in the Midwest.

They said the population in the five Calico herd management areas is three times what the range can handle.

The state's wildlife agency sides with the BLM, saying the mustangs have "severely degraded" the range and adversely affected native wildlife.