*The Bush administration has scaled back plans to quickly build a "virtual fence" along the U.S.-Mexico border, delaying completion of the first phase of the project by at least three years and shifting away from a network of tower-mounted sensors and surveillance gear, federal officials said yesterday. Technical problems discovered in a 28-mile pilot project south of Tucson prompted the change in plans, Department of Homeland Security officials and congressional auditors told a House subcommittee.*The virtual fence was to complement a physical fence that the administration now says will include 370 miles of pedestrian fencing and 300 miles of vehicle barriers to be completed by the end of this year. The GAO said this portion of the project may also be delayed and that its total cost cannot be determined. The president's 2009 budget does not propose funds to add fencing beyond the 700 or so miles meant to be completed this year.