US cops pulls gun on unarmed passenger during traffic stop

US police have been forced to explain why an officer kept his gun trained on an unarmed passenger for almost 10 minutes during a traffic stop.

Video posted to Facebook on July 26 shows the Campbell police officer point his gun at a man on Highway 101 in California while a female driver recorded the incident on her phone.

For almost 10 minutes the highway cop keeps his weapon pointed at the passenger, who eventually loses his temper and tells him to "get that f---ing gun off me bro".

At one point the driver urges the officer to at least swap his handgun for a taser.

Campbell police said in a statement cited by NBC that the phone footage only shows one side of the story and that the officer's body camera provides a clearer picture of the incident.

However, police have refused to release the footage.

Police claim that while the officer was walking back to his bike the man reached under his seat, prompting him to draw his weapon.

"It was out of the ordinary for the passenger to reach down there. And based on training, the officer made the decision to pull out his gun and wait for back up," police said in a statement.

US police are trained to keep their weapons drawn in a threatening situation if they are alone until backup arrives.

No charges have been brought against the officer, however, the driver was charged with speeding.