The Air Force refused to comment when contacted by AFP. The new aircraft was reportedly built by Northrop Grumann, the company behind the Global Hawk and the X-47B drones, which landed on air craft carriers for the first time this summer.
The US company may have obtained in 2008 a secret contract on the order of $2 billion to develop the latest drone, according to Aviation Week.
An artistic rendering of the RQ-180 on the cover of the magazine shows a craft with striking resemblance to the X-47B, in particular in lack of rear stabilizer and its so-called "batwing" shape.
It was developed for intelligence, surveillance and reconnaissance (ISR) missions, but "could also be capable of electronic attack missions," the magazine said.
"It is similar in size and endurance to the Global Hawk," which can fly for 24 hours up to 1,200 nautical miles (2,000 kilometers) from its base.
A first generation of unmanned aircraft, the non-stealthy Reapers and Global Hawks, were used in Afghanistan and Iraq, but they were deemed too vulnerable in enemy territory equipped with powerful anti-aircraft defenses.Now the Air Force is slowly turning to stealth drones, better at passing safely over unfriendly territory.
In December 2011, a spy drone that had until then been secret, the RQ-170 Sentinel, crashed 155 miles (250 kilometers) inside Iranian air space.
The unmanned craft, which had taken off from Afghanistan, was on a mission to observe Iran's nuclear sites for the CIA, according to US press reports.