Billionaire Elon Musk criticised United States President Donald Trump's senior trade adviser Peter Navarro as "truly a moron" and "dumber than a sack of bricks" overnight in a growing rift over the US tariff policy that has rocked the world.
The public spat came after Navarro described the Tesla boss and Department of Government Efficiency chief as "not a car manufacturer" but "a car assembler" who relies on imported parts.
Musk, the world's richest person, has previously signalled his opposition to Trump's new import tariffs that have roiled markets.
"Navarro is truly a moron. What he says here is demonstrably false," Musk wrote on his X social network, under a clip of Navarro saying Tesla imported batteries, electronics and tires, and wants the cheap foreign parts.
Musk doubled down in a series of other messages, saying: "Tesla has the most American-made cars. Navarro is dumber than a sack of bricks."
Musk also dubbed him "Peter Retarrdo" and said Navarro "should ask the fake expert he invented, Ron Vara", referring to a fictional pundit Navarro quoted in a series of books and a policy memo, using an anagram of his own name.
'Boys will be boys'
The White House played down the row.
"Boys will be boys and we will let their public sparring continue," White House press secretary Karoline Leavitt told a briefing when asked if the spat would harm the White House's messaging on tariffs.
The South African-born tycoon recently backed the idea of a free-trade zone between North America and Europe — a wish at odds with Trump's flagship tariffs.
Trump has ruled out any pause in his aggressive stance despite retaliatory action from China and signs of criticism from within his Republican Party.
But there have also been conflicting messages from within the White House itself.
A long-time China critic, Navarro has been one of the most hardline voices on tariffs and targeted Musk himself in an interview with CNBC.
"When it comes to tariffs and trade, we all understand in the White House, and the American people understand, that Elon's a car manufacturer. But he's not a car manufacturer — he's a car assembler in many cases," Navarro said.
"If you go to his Texas plant ... the batteries come from Japan and from China, the electronics come from Taiwan."
The row came a day after Navarro insisted in an opinion piece in the Financial Times that the tariffs were "not a negotiation", only for Trump to admit later that he was open to some negotiations.
The spat is unusual due to the complex loyalties involved.
