The big reveal of Tesla’s electric pick-up went embarrassingly wrong when the supposedly impact-proof windows smash, leaving a flustered Elon Musk to flounder through the rest of his presentation in front of a badly damaged vehicle.

The Tesla co-founder unveiled the all-electric battery-powered Tesla Cybertruck in California on Thursday, daring staff to hit the vehicle with sledgehammers and showing a video of it withstanding bullets shot from a 9mm gun.

But the demonstration of the vehicle’s indestructible windows didn’t appear to go entirely to plan after one assistant threw a steel ball bearing at the truck — only to see the armoured glass smash.

An expletive could be heard at the Tesla Design Center and as his assistant laughed nervously, Musk said: “Well, maybe that was a little too hard.”

A second attempt fared little better however, and another window was left badly damaged.

“It didn’t go through,” said a clearly uncomfortable Musk, who was forced to push on through the remainder of the chaotic launch with the two smashed windows in full view.

The industrial-looking Cybertruck — covered in the same steel alloy Musk plans to use for his SpaceX rocket — will have a starting price of $39,900 and can go from 0 to 100 kilometres (62 miles) per hour in about three seconds, the Tesla chief executive claimed.

No date has been given for its release but analysts said it would not be ready before the end of 2021 at the earliest.

Tesla dominates the global electric car market and has an especially firm grip on the United States.