The bike can be customised for different operations, with carriers and camouflage.

According to its makers, Virginia-based Logos Technologies, the bike's louder mode would be slightly louder than the average vacuum cleaner, reaching up to 75 decibels.

The company also says it Silent Hawk could travel over difficult terrain on its hybrid engine over a sustained period at 55 miles per hour (88km/h).

The combustion engine will also be removable, which means Silent Hawk can become all-electric, and also shed weight or take out problem parts.

On its own, the bike's battery can power it for up to 50 miles (80km). However, the concept is still under development and further specifications have yet to be announced.

Silent Hawk is based on Alta Motors' electric racing bike, the RedShift MX (pictured). It uses Alta's chassis, while the hybrid engine is being developed by Logos

The Defense Advanced Research Projects Agency (Darpa) began the motorcycle project last year, and has now granted its makers an award to develop it further.

Logos says it now plan 'to proceed with an aggressive Phase II program plan, with the goal of developing and testing the first operational prototype in only 18 months.'

Silent Hawk is based on Alta Motors' electric racing bike, the RedShift MX. It uses Alta's chassis, while the hybrid engine is being developed by Logos.

The U.S. Special Operations Command previously tried to use an all-electric Zero MMX bike for the same purpose, but the battery only lasted two hours.

It's not just commandos will soon be receiving steal motorbikes. In August, it was announced that police forces could use the bikes to approach criminals undetected.

The bike, designed by Zero Motorcycles in northern California, has a top speed of up to 98 mph (158 km/h), allowing police to chase criminals down if the stealth approach fails.

It's not just commandos will soon be receiving steal motorbikes. In August, it was announced that police forces could use electric bikes (concept pictured) to approach criminals undetected.