WASHINGTON — Taxpayers have shelled out at least $15.1 million per mile for 53 miles of “virtual fence” built to secure the U.S.-Mexico border, more than 12 times the original estimate.

The federal government set aside $833 million for the fence of cameras, sensors and other barriers in 2007, and the vast majority of that money, at least $800 million, has been spent on a sliver, in Arizona, of the nearly 2,000-mile southern border. About $20.9 million has been used on the northern border.

The money was supposed to buy virtual fence for 655 miles of border in Arizona, New Mexico and a slice of Texas, at a cost of about $1.2 million per mile.

The fence, developed as part of a border security plan under President George W. Bush, was supposed to monitor most of the southern border with Mexico by 2011. Now, the 53 miles in Arizona is expected to be done by the end of the year.

Additionally, the expected capabilities of the virtual fence have shrunk.

The Homeland Security Department has suspended the project while it decides what to do next. Some officials say some good has come from the project, but they question the cost for those capabilities.