American commanders in Iraq are urging Pentagon chiefs to authorise the deployment of newly-developed heat wave guns to disperse angry crowds or violent rioters.
In pictures: How I was zapped by a heat wave gun
But the plea for what senior army officers believe could prove a valuable alternative to traditional firepower in dangerous trouble-spots has so far gone unanswered.
The ADS can target crowds from 750 metres away
Washington fears a barrage of adverse publicity in the suspicious Muslim world and is concerned that critics will claim the invisible beam weapons were being used for torture.
Now the US military directorate charged with developing non-lethal weapons, which has invested more than a decade developing the Active Denial System (ADS), has launched a concerted effort to convince both the public and its own bosses at the defence department of the device's merits.
"With brand new technology like this, perception is everything," said Col Kirk Hymes, a former Marine artillery officer who heads the directorate.
He added that tests were almost complete and the first ADS, also known as the Silent Guardian, could be deployed early next year if the Pentagon allows. The decision is so sensitive that it is expected to be made personally by the defence secretary, Robert Gates, who sent senior representatives to the demonstrations.
Raytheon, the company contracted to manufacture the prototype, has also received interest from several undisclosed European countries. The machine displayed last week cost about $10 million to build, but the directorate believes that the ADS can be put into production for $2-$5 million (£1-2.5 million) per device.
Col Hymes told observers at a demonstration that the system was a safe and effective alternative to plastic bullets, which can cause injury and sometimes death and are effective only up to 75 metres.
The heatwave weapon can, by contrast, target troublemakers from 750 metres. It works by dispatching high-powered radio waves from a vehicle antenna, similar to a satellite television dish, causing the molecules in a target's skin to vibrate violently, creating a burning sensation.
"We are pretty good at shouting and intimidating people and we have been perfecting the art of lethal warfare since Cain and Abel," he said. "But in places like Iraq we are re-learning that we need a response in the spectrum between shouting and shooting. The ADS provides this."
But he added: "This is not something we want to roll out and deploy and surprise people. We know we need to educate the public."
In fact the development of the weapon only became public after the Sunshine Project - a Texas-based group that campaigns against biological and chemical weapons - pushed for disclosure under the Freedom of Information Act.
In pictures: The Telegraph's Philip Sherwell is zapped by a heat wave gun
The group's director, Edward Hammond, said: "If we are not prepared to use it as a crowd control technique on our own citizens, then we really shouldn't be using it in Iraq either."
Marc Garlasco, a former Pentagon intelligence officer who is senior military analyst for the Human Rights Watch campaign group, was among those invited to feel the device's impact at a recent demonstration.
He said: "If I had the option of being shot by a bullet or this, I would choose this - but still not enough is known about it. This is novel technology. We're talking about bringing science fiction into reality and it's critical to have open discussion."
He added: "People understand what happens when you get shot with a gun, but with the "pain-ray" there's still uncertainty. When it's used, the military is going to have to deal with a public backlash because I'm sure there will be claims of medical problems by the people it's been used upon, real or not."
"We are talking about young soldiers having this in their hands. If we upset the civilian population in Iraq, whether by killing, by torture or by misusing this, it will have a strategic effect on the US's ability to execute effective operations."
Col Hymes said that all ADS operators were given a six-week training course that covered sophisticated crowd control techniques as well as handling the technology.