US Defense Secretary Robert Gates expressed concern over Iran's aerial drone program, saying the weapons could fall into the hands of terrorists. "Countries like Iran are developing their own UAVs and already have a UAV capability," Gates told the Senate Appropriations Committee, using the acronym the military uses for drones -- Unmanned Aerial Vehicles. "That is a concern, because it is one of these areas where -- if they chose to, in Iraq, in Afghanistan -- they could create difficulties for us."