Elon Musk dubbed one of Donald Trump's advisers "moron," in the latest spat between the South African-born billionaire and members of the US president's administration.
Trade adviser Peter Navarro made disparaging comments aimed at Musk, in which he said Musk was "not a car manufacturer".
"He's a car assembler, in many cases," Navarro added in a CNBC interview on Monday.
The owner of Tesla and SpaceX fired back on his platform X, saying Navarro was "dumber than a sack of bricks".
Musk, whose recent comments hinted at his disapproval of US tariff policies, which have roiled the global markets this week, added that Navarro's comments were "demonstrably false".
"These are obviously two individuals who have very different views on trade and on tariffs," White House spokesperson Karoline Leavitt said on Tuesday.
"Boys will be boys, and we will let their public sparring continue," she quipped.
Rumours of a growing schism between the world's richest person and Trump were made worse by reports of Musk attempting — and failing — to convince the US president to hold back on sweeping global tariffs he introduced last week, in an event Trump dubbed "Liberation Day".
Musk, who also leads the unofficial Department of Government Efficiency, or DOGE, is said to be set to leave the administration soon.
Trump's vice president, JD Vance, tried to quell the reports of growing tensions between the duo by saying last week Musk will remain "a friend and an adviser".
“Elon came in and we said: ‘We need you to make government more efficient, we need you to shrink the incredible fat bureaucracy that thwarts the will of the American people but also costs way too much money,” Vance said in an interview with Fox News last Thursday.
“We said, ‘That’s going to take about six months,' and that’s what Elon signed up for, but of course, he’s going to continue to be an adviser and by the way, the work of DOGE is not even close to done, the work of Elon is not even close to done.”
Supporters continue to speak out
Meanwhile, the number of influential Trump allies who have cast doubts on his levies has grown in recent times.
Barstool Sports owner Dave Portnoy, hedge fund manager Bill Ackman and conservative podcaster Joe Rogan all weighed in against the tariffs.
Rogan, one of the US' most popular podcasters who endorsed Trump on the eve of last year's election, said in March that Trump's feud with Canada was “stupid” and bemoaned the fact that Canadians “booed us over tariffs" during professional sporting events featuring teams from both countries.
Rogan has recently broken with Trump in other areas, including over wide-ranging deportations, referring to a recent operation to detain immigrants as “horrific”.
Navarro, who is one of the biggest backers of Trump's trade policies, has called the US trade deficits “the sum of all cheating’’ by other countries.
The tariffs, which analysts said were questionable in nature and stemmed from a warped idea of world trade tied to Trump's preoccupation with trade deficits, have panicked global financial markets, raised the risk of a recession and broken the political and economic alliances that made much of the world stable for business after World War II.
