US draws up plans for nuclear-powered drones: Report

"It's pretty terrifying prospect," said Chris Coles of Drone Wars UK, which campaigns against the increasing use of drones for both military and civilian purposes.

"Drones are much less safe than other aircraft and tend to crash a lot. There is a major push by this industry to increase the use of drones and both the public and government are struggling to keep up with the implications," he added.

The blueprints for the new drones have been developed by Sandia National Laboratories - the US government's principal nuclear research and development agency - and defense contractor Northrop Grumman.

The drones have been designed to increase flying time "from days to months" while making more power available for operating equipment, according to a project summary published by Sandia.

A halt, however, has been called to the work for now, due to worries that public opinion will not accept the idea of such a potentially hazardous technology, with the inherent dangers of a crash - in effect turning the drone into a so-called dirty bomb, The Guardian reported on Monday.

The project’s research summary, meanwhile, said the results "were to be used in the next generation of unmanned air vehicles used for military and intelligence applications", where they "would have provided system performance unparalleled by other existing technologies."

Coles expressed his concern about the ramifications of the projects, saying the increasing sophistication of drones poses many threats.

"As they become low-cost, low-risk alternatives to conventional warfare, the threshold for their use will inevitably drop. The consequences are not being thought through," he said.

Washington has increasingly turned to unmanned aircraft to carry out strikes in several countries, including Pakistan, Yemen, and Somalia.

The US says the operations target militants, although surveys show most of the victims are civilians.

The aerial attacks were initiated by former US President George W. Bush but have been escalated under President Barack Obama.