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The US army says it has mothballed plans to deploy a robot developed in conjunction with Google because it is "too loud".

The Legged Squad Support System - referred to by some as "the big dog" - is capable of carrying 400lbs (181.4kg) of equipment over rugged terrain.

But the US Marines now say its petrol-powered engine is too noisy for them to use in battle.

Google has long said it planned to move away from its military contracts.

The LS3 was developed by Boston Dynamics - a robotics firm acquired by Google in 2013 - as part of a tie-up with the Pentagon's research arm, the Defence Advanced Research Projects Agency (Darpa).

The robot can follow troops on foot through rugged terrain, carrying their gear.

It can also interpret verbal and visual commands.

However, after a major field trial in 2014, flaws in the robot also became apparent, according to Kyle Olson, a spokesman for the Marines' Warfighting Lab.

"There was the challenge of seeing [its] potential... because of the limitations of the robot itself," he told .

"They took it as it was: a loud robot that's going to give away their position."

The machine, which has a gas-powered engine, is said to emit a lawnmower-like noise that would be unviable in combat situations.

It is also thought to be difficult to repair.

In response, Boston Dynamics did create a quieter, electric-powered alternative, called Spot. But despite successful trials in September 2015, the Marines have decided not to take it forward either.

This, they said, was because Spot is smaller, can only carry up to 40lbs, and lacks the automation capacity of the LS3.

Google said as far back as 2013 that it planned to move away from its military contracts, which it inherited as part of its acquisition of the company.

The tech firm has said it intends to develop robots for .

Noel Sharkey, co-director of the Foundation for Responsible Robotics, told the ´óÏó´«Ã½: "Spot ... lacks the autonomous operation of Big Dog, but that really is not so much of a problem and would not require a vast amount of research.

"The problem is that to take the extra steps need to upgrade the battery-driven Spot to the level of Big Dog could require a couple of years development or more and thus a new Darpa contract.

"So, what this looks like is a face saving statement by the Marine Corps to make it look like they are dumping Google/Boston Dynamics before they they got dumped themselves."