A robot modeled after the cheetah, the world's fastest land animal, broke the speed record for a legged robot, U.S. officials announced Monday

The robot achieved speeds of 18 mph (29 km/h) on a treadmill, breaking the previous record of 13.1 mph (21 km/h) set by in 1989, according a to press release from the Defense Advanced Research Projects Agency (DARPA), an agency of the U.S. Department of Defense.

Engineering and robotics design company Boston Dynamics built the robot with funding from DARPA. Boston Dynamics first announced the robot in February 2011 with the aim to have the robot fully operational by 2015.

The robot can achieve high speeds the same way a cheetah does, according to CNET. Flexing and unflexing their spines allows cheetahs to take longer strides and causes their legs to act like a spring, propelling the cheetah forward, according to the Cheetah Conservation Fund.

There's no fundamental reason why [the robot] can't go as fast as [a real cheetah], but it will take a while to get there, Boston Dynamics President Marc Raibert told The Boston Herald in 2011.

Cheetahs can run between 70 and 75 mph (112 and 120 km/h).

The robot is currently powered by an attached pump but Boston Dynamics engineers will take the robot off the treadmill and test a free-running prototype soon, according to a DARPA press release.

DARPA developed the robot as part of its Maximum Mobility and Manipulation (M3) program, which began in March 2011. Researchers are trying to overcome current limitations of robotic designs - high cost, long manufacturing times and poor mobility.

If these limitations were overcome, robots could assist in the execution of military operations far more effectively across a far greater range of missions, DARPA says on its website.

The cheetah isn't the only robot that DARPA and Boston Dynamics are working on.

The BigDog is a robotic mule capable of carrying 340 pounds (154 kg) up a 35 degree slope, according to Boston Dynamics.

Atlas is another robot, one modeled after a headless human. Atlas will be able to walk, crawl and slip through narrow passages normally inaccessible once completed, according to Wired.

No word on when either of these are scheduled to be finished.

Noel Sharkey, professor of artificial intelligence and robotics at the University of Sheffield, who is not involved in the production of the robots, told the BBC the robots are impressive. However, he said there is still one problem that needs to be addressed before deploying them in the battlefield.

The biggest concern about this is that no artificial intelligence system can distinguish between civilians and enemy combatants, and so if this was operating on its own it would fall foul of the laws of war, he said.