A US Border Patrol agent monitors the surroundings from his vehicle near the San Ysidro port of entry along the US-Mexico border near San Diego, California on April 4, 2013. The barrier separating the two countries known to many as the 'border fence' or the 'border wall' is in reality several barriers, designed to prevent illegal movement across the border, backed by supporters and criticized by opponents. AFP PHOTO/Frederic J. BROWNFREDERIC J. BROWN/AFP/Getty Images