US-Mexico 'virtual' fence on hold
The US is freezing funding for a "virtual" fence designed to detect people illegally crossing the Mexico-US border, after a series of problems.
US Homeland Security Secretary Janet Napolitano said spending was being halted until the project was reviewed.
In addition, $50m (£32m) is being redirected to other tested technology.
The "virtual" fence, which currently just covers part of the Arizona-Mexico border, was designed as a network of cameras, sensors and radar.
The programme was launched by the Bush administration in 2005 and was supposed to be in operation along the 2,000 mile (3,200km) border by 2011.
The aim is to allow Border Patrol agents to monitor the border via cameras, ground sensors and radars and respond when crossings by illegal immigrants or smugglers are detected.
"Not only do we have an obligation to secure our borders, we have a responsibility to do so in the most cost-effective way possible," Ms Napolitano said on Tuesday.
"The system of sensors and cameras along the Southwest border known as SBInet has been plagued with cost overruns and missed deadlines."
Ms Napolitano said $50m would be reallocated to other tested, commercially available security technology including mobile surveillance, thermal imaging devices, mobile radios, cameras and laptops for vehicles used by Border Patrol agents.
No further money will be spent on expanding the project beyond Arizona until a reassessment is completed.
Arizona Senator John McCain, who has described SBInet as a "complete failure", welcomed the move.
"Napolitano has decided to instead turn to commercial available technology that can be used to immediately secure our border from illegal entries," he said.
The House of Representatives Homeland Security Committee is due to hold a hearing on the virtual fence project this week.
Its chairman, Bennie Thompson, said Ms Napolitano's decision showed that the programme "needs better management and stronger oversight".
Among the problems, the radar system had difficulties in distinguishing between people and trees when it was windy, while it took too long to send information from the ground back to a command centre.
Boeing, which manages the project, said it was "fully committed to delivering border-security technology that successfully assists" the homeland security department.
The issue of border security has been given added importance by the level of drug-related violence in Mexico.