ech entrepreneur Elon Musk on Thursday said he had received "verbal" approval to start building an ultra-high-speed underground transport system linking New York and Washington that would cut travel time between the cities to about half an hour.
He offered no details on what entity had greenlighted the project that could result in the world's longest tunnel.
Musk, the chief executive of electric car maker Tesla and rocket company SpaceX, is seeking to revolutionize transportation by sending passengers and cargo packed into pods through an intercity system of giant vacuum tubes known as the "hyperloop".
Officials in Washington and New York said they had not approved any project, and under federal rules Musk would need extensive environmental and building permits to mount such an ambitious project.
Musk recently started an enterprise called the Boring Company to build transport tunnels for the system, which he says would be far faster than current high-speed trains and use electromagnetic propulsion.
In tweets on Thursday Musk said he had "just received verbal government approval for the Boring Company to build an underground NY-Phil-Balt-DC hyperloop. NY-DC in 29 mins."
Amtrak's high-speed Acela train currently takes nearly three hours to cover the roughly 220 miles (355 km) between the two cities, assuming no delays.
Asked for details on who had offered approval, the Boring Company said in a statement it expected "to secure the formal approvals necessary to break ground later this year."
Still a lot of work needed to receive formal approval, but am optimistic that will occur rapidly
Musk also tweeted that a first set of tunnels would be to "alleviate greater LA (Los Angeles) urban congestion," adding that the company would also "probably" do a loop from Los Angeles to San Francisco, and another in Texas.
"City center to city center in each case, with up to a dozen or more entry/exit elevators in each city," he wrote.
Musk acknowledged there was still a "lot of work" to do before formal approval was granted, but said he was optimistic.
Signaling that Musk's tweets may be premature, the press secretary for New York City Mayor Bill de Blasio tweeted a reply: "This is news to City Hall."
Musk said in a later tweet that supporters should lobby government officials. "If you want this to happen fast, please let your local & federal elected representatives know. Makes a big difference if they hear from you," he wrote.
Last month, Musk tweeted that he had "promising conversations" about a tunnel network with Los Angeles Mayor Eric Garcetti.
