Elon Musk has said he has received permission to build an underground east coast  "hyperloop" that will connect New York and Washington DC in just 29 minutes.

Mr Musk, best known for his electric car company and for his space venture Space X, said he had received verbal permission for his infrastructure and tunnelling firm, the Boring Company, to build a subterranean transportation system.

Mr Musk, who has previously made claims that many have considered wild, did not say who he had received permission from, or the nature of the “verbal agreement”.

Just received verbal govt approval for The Boring Company to build an underground NY-Phil-Balt-DC Hyperloop. NY-DC in 29 mins.

— Elon Musk (@elonmusk) July 20, 2017

“City centre to city centre in each case, with up to a dozen or more entry/exit elevators in each city.”

Earlier this month Mr Musk announced the Boring Company’s Godot machine has begun its digging operation in the car park of the SpaceX building in LA.

Mr Musk first proposed the electromagnetic tube system in 2013. Earlier this year the California tech company Hyperloop One unveiled a plan for a NY-to-DC system.

Many people on social media asked Mr Musk who had given him permission for the project but he refused to answer.