The US military and intelligence agencies deploy thousands of unmanned vehicles in the air and on the ground, including Predator and Reaper drones used to bomb militants in Pakistan.

The robots include:

MQ-1 PREDATOR: The Predator is a propeller-powered drone that can fly at an altitude of up to 7,620 meters (25,000 feet) for up to 24 hours, with video cameras and radar sending back data to a control center thousands of miles away.

Originally designed for surveillance and used heavily in Iraq and Afghanistan, the Predator can be armed with two Hellfire anti-tank missiles. Slightly smaller than a Cessna plane, the Predator is about eight meters (27 feet) long with a wingspan of more than 14 meters (48 feet). The aircraft, made by General Atomics Aeronautical Systems, cruises at a speed of 70 knots.

MQ-9 REAPER: The Reaper is a larger, more powerful and heavily-armed version of the Predator that can be equipped with precision-guided bombs and Hellfire missiles. Manufactured by the same firm that makes the Predator, the plane is 11 meters (36 feet) long with a wingspan of 20 meters (66 feet). It can cruise at 200 knots and reach an altitude of up to 15,240 meters (50,000 feet).

RQ-4 GLOBAL HAWK: Designed to replace the Cold War-era U2 spy plane, the jet-powered Global Hawk flies reconnaissance and surveillance missions at high altitude using sophisticated sensors and cameras. The plane, made by Northrop Grumman, can fly for up to 35 hours at an altitude of 18,288 meters (60,000 feet) and reach a speed of 340 knots.

RQ-11 RAVEN: The smaller Raven can be carried in a backpack and is launched into the air by hand, allowing soldiers to look at video from around a corner or over the next hill. Weighing in at 1.9 kilograms (4.2 pounds) and less than a meter long, the Raven can fly for up to 80 minutes and reach a speed of 52 knots. Manufactured by Aeroenvironment, the plane was first deployed in 2004.

PAKBOT: An unmanned ground vehicle equipped with cameras, sensors and a mechanical arm, the Pakbot can climb up stairs and over rocks with its tank treads. Resembling the robot in the animated film "Wall-E," the vehicle comes in different sizes and can weigh from six to 20 kilograms (14 to 42 pounds). The vehicle lacks the autonomy of an unmanned plane, and has to be steered remotely by a soldier. The Pakbot has been used mainly to search for and dismantle explosives in Iraq and Afghanistan.

SWORDS: The Special Weapons Observation Remote Direct-Action System (SWORDS) is a ground robot designed to be armed with an M-16 rifle, a machine gun or a rocket launcher. Three robots have been built so far and reportedly the military and the contractor, Foster-Miller, are working out remaining technical problems. The US Army has reportedly used the SWORDS robots for surveillance and guard missions in Iraq but the vehicles have not fired a shot in combat.

MULE: The military is testing and developing other armed ground robots, including the MULE -- a vehicle about the size of a Humvee armed with anti-tank missiles and a turret-mounted machinegun. The Multifunction Utility/Logistics and Equipment (MULE) robot is supposed to fire only when a human operator remotely pulls the trigger. The MULE could be ready for deployment as soon as 2014.