The truck's windows were smashed during a demonstration supposed to show how hard they were to break.

Mr Musk was heard to swear before joking: "Room for improvement."

The truck was unveiled in Hawthorne, California, where its stainless steel, angular design was greeted with cheers but also bemusement.

"People probably won’t get past the looks of it," said Jessica Caldwell, from vehicle marketplace Edmunds.

"It looks like a truck version of the DeLorean from Back To The Future."

The pickup market represents a significant opportunity for Tesla as it improves its battery technology, meaning carrying heavier loads over long distances is now practical.

According to Edmunds, large trucks have accounted for 14.4% of new vehicle sales up until October this year, compared to 12.6% in 2015. The vehicles have an average selling value of more than $50,000.

Tesla's truck will be sold starting at $39,900 (£30,900), a model which has a range of 250 miles (402km), while the most expensive model, at $69,900, will have a range of 500 miles. The truck will seat up to six adults and haul a payload of 3,500lbs, Tesla said.

Mr Musk said pre-orders would start immediately, with production starting in late 2021 - though the 48-year-old has a history of missing his own deadlines.

The Cybertruck's launch will undoubtedly be overshadowed by the "fail", Ms Caldwell said.

It happened during a segment displaying how the car's stainless steel exterior, and metal windows, could withstand bullets and sledgehammers. However, when Tesla's head of design, Franz von Holzhausen, threw a metal ball at the front left window, it smashed. As too did the rear left.

"It didn’t go through, that’s a plus side," Mr Musk said.

"We threw wrenches, we threw literally the kitchen sink at the glass and it didn’t break. For some reason it broke now… I don’t know why."

At the time of writing, Tesla stock price was mostly unchanged in after-hours trading.