Aircraft manufacturer Boeing successfully tested the weapon on a one-hour flight during which it knocked out the computers of an entire military compound in the Utah desert.
It is thought the missile could penetrate the bunkers and caves believed to be hiding Irans suspected nuclear facilities. But experts have warned that, in the wrong hands, the technology could be used to bring Western cities such as London to their knees.
During Boeings experiment, the missile flew low over the Utah Test and Training Range, discharging electromagnetic pulses on to seven targets, permanently shutting down their electronics.
