Shares of Elon Musk’s electric vehicle company have plunged more than 14 per cent, knocking about $US150 billion ($230 billion) off Tesla’s market valuation as investors fear his dispute with US President Donald Trump will hurt the company.

Tesla closed down more than 14 per cent as a disagreement over the US president’s budget bill turned nasty.

After Musk said that Trump wouldn’t haven’t gotten elected without his help, Trump implied that he may turn the federal government against his companies, including Tesla and SpaceX.

“The easiest way to save money in our Budget, Billions and Billions of Dollars, is to terminate Elon’s Governmental Subsidies and Contracts,” Trump wrote on his social messaging service Truth Social. “I was always surprised that Biden didn’t do it!”

The shares tanked earlier this year as Musk’s association with DOGE damaged the car company’s brand. Shares rallied when he promised in April to focus more on Tesla.

Now, Wall Street is worried about Trump’s hitting back at Musk through Tesla.

“Trump is tit for tat. If Musk tries to mess up Trump’s bill, Trump won’t be Mr Nice Guy” when it comes to self-driving cars, which Musk acknowledges are a key to Tesla’s future, said Dan Ives of Wedbush Securities.

Tesla’s heavy losses partially reverse a big run-up in the eight weeks since Musk confirmed that Tesla would test an autonomous, driverless “robotaxi” service in Austin, Texas, this month.

Investors fear Trump might not be in such a rush to usher in a future of self-driving cars in the US, and that could slam Tesla because so much of its future business depends on that.

“The whole goal of robotaxis is to have them 20 or 25 cities next year,” Ives said. “If you start to heighten the regulatory environment, that could delay that path.”

Trump’s threat to cut government contracts seem targeted more to another of Musk’s businesses, SpaceX, his privately held rocket company that received billions of dollars to send astronauts and cargo to the International Space Station, provide launches and do other work for NASA.

The company is currently racing to develop a mega rocket for the space agency to send astronauts to the moon next year.

A subsidiary of SpaceX, the satellite internet company Starlink, appears to also have benefited from Musk’s once-close relationship with the president.

On a trip with Trump to the Middle East last month, Musk announced that Saudi Arabia had approved his satellite service for aviation and maritime use.

Though its not clear how much politics has played a role, a string of other recent deals for the company in Bangladesh, Pakistan, India and elsewhere has come as Trump has threatened tariffs and sent diplomats scrambling to please the president.

One measure of SpaceX’s success: A private financing round followed by a private sale of shares recently reportedly valued it at $US350 billion, up from an estimated $US210 billion just a year ago.

Tesla shares initially got a lift from his support of Trump. In the weeks after Trump was elected, Tesla shares surged, hitting an all-time high on December 17.

But they gave back those gains during Musk’s time as head of a government cost-cutting group as Tesla’s reputation took a hit. They’ve recently popped higher again after Musk vowed to focus much more on Tesla and its upcoming launch of driverless taxis.