Hold the phone: Is that a gun?

To the plain eye, this smartphone is nothing out of the ordinary  - but what's frightening is it's actually a fully functional firearm.

The 380-calibre handgun, which unfolds from a convincing phone shape, is causing grave concern in the United States.

The weapon is expected to go on sale soon for $395 (NZ$556), and has already been reserved by more than 12,000 Americans.

The design is worrying law enforcement officials, with police reportedly on high alert in expectation of the guns being smuggled outside of the US.

On Monday New York senator and gun control advocate Charles Schumer called on the department of justice and the bureau of alcohol, firearms and explosives, to investigate whether the gun violates federal law.

Ideal Conceal CEO Kirk Kjellberg says it allows responsible owners to carry a gun more freely.

“Some people would really take serious issue in a workplace or somewhere else to see a gun on you. I think it gives people an opportunity to avoid that conversation.”

The double-barrelled pistol's being advertised on Ideal Conceal's website as a lightweight piece that will "easily blend in with today's environment".

"Ingeniously designed to resemble a smartphone, yet with one click of the safety it opens and is ready to fire," the website reads.

The phone has a belt-clip accessory, allowing users to hide it in plain sight.

The weapon is normally carried with the safety on, Ideal Conceal says, with only the grip hiding the trigger underneath.