The National Wild Horse Foundation founded by Mrs Pickens to help drive the proposal has been told by the Bureau of Land Management (BLM) that federal land being considered for part of the sanctuary cannot be used because the government does not want wild horses in areas where they did not exist when the Free Roaming Horses and Burros Act was enacted.
The sanctuary proposal was put forward by Mrs Pickens, wife of the Texas oil tycoon T. Boone Pickens, after the bureau revealed it was considering euthanizing horses as a way to stem the escalating costs of caring for the 30,000 wild horses and burros now held in captivity.
There are now roughly as many horses held in captivity as roam the hundreds of millions of acres of rangelands.
The numbers have grown because of the bureau's regular mustering of wild horses to protect natural resources from overgrazing by wildlife, cattle, and horses.
The horses are offered for adoption but every year thousands are not adopted and are sent to holding corrals.
The foundation proposes acquiring a million acres, combining both private and bureau lands, to return the captured horses to their natural rangelands and roaming lifestyle.
"Why isn't the BLM working enthusiastically with the foundation to save millions of taxpayer dollars and relocate captive horses to a ranch with plenty of open space, water and feed?" Mrs Pickens asked on her website.
The bureau's costs in 2009 are expected to be $US33 million for horses in its numerous holding facilities.
By 2014, the bureau has estimated that its costs for the wild horse programme will exceed $US85 million a year.
The foundation estimates that a single large sanctuary would save taxpayers as much as $US700 million otherwise spent on various horse-holding pens and pastures over the 10-year period ending in 2020.
The bureau pays ranchers about $US500 an animal per year to provide long-term holding for the 22,000 federally owned horses in private pastures in Kansas and Oklahoma. It pays about $US2000 per animal per year, to feed 9000 wild horses in federal pens.
However, the bureau told the National Wild Horse Foundation it wants the foundation to own the wild horses so it (the bureau) could terminate its financial responsibility for horses transferred to the foundation ranch.
"Unfortunately, the foundation cannot care for and protect 30,000 wild horses without a stipend and remain solvent," Mrs Pickens said. "The federal government must remain part of the solution created by removing the wild horses from their homeland."
Backers of the sanctuary proposal have been urged to write letters in support of the plan to several key political figures and office holders. A list can be found here.