Australia could become a test ground for another of Elon Musk's massive infrastructure projects after the maverick billionaire tweeted a "bargain" price to build a tunnel through a mountain to solve Sydney's traffic woes.
Musk in 2017 made a Twitter pitch -- and followed through with the offer -- to build what was the world's biggest battery in an Australian state to solve its severe energy crisis.
The entrepreneur behind electric carmaker Tesla has most recently turned his sights on tackling city traffic via low-cost tunnels created by his Boring Company, and in December unveiled a sample project near Los Angeles.
So when an Australian politician tweeted at Musk on Wednesday about the costs of drilling through a mountain range north of Sydney, he responded quickly.
"I'm a lawmaker in Sydney, which is choking with traffic. How much to build a 50km tunnel through the Blue Mountains and open up the west of our State?," asked New South Wales state MP Jeremy Buckingham.
"About $15M/km for a two way high speed transit, so probably around $750M plus maybe $50M/station," Musk replied late Wednesday, with his response liked more than 22,000 times on Twitter.
He has more than 24 million followers on the social media platform.
Another billionaire, Mike Cannon-Brookes, who founded Australian software startup Atlassian, weighed in on the exchange, saying the estimated price tag "sounds like a bargain for Sydney".
The population of the Sydney region has grown by around 25 percent since 2011 to reach 5.4 million, out of a national population of 25 million, and road congestion is a major concern.
There was no indication the exchange of tunnel tweets would lead to any quick action, but it could bring some needed positive publicity for Musk.
Musk has risen to prominence with a series of ambitious ventures, particularly Tesla, but has also drawn plenty of criticism for some volatile behaviour.
He waged a public battle with a rescuer who helped save a group of boys trapped in a cave in Thailand last year, calling him a "pedo guy" after the Brit slammed his idea of building a mini-submarine to save the children as a public relations stunt.
Meanwhile, riders who have tested out Boring's prototype tunnel -- where cars are lowered by lifts then slotted into tracks and propelled along at high speeds -- have complained of a bumpy journey.