Elon Musk took another jab at President Donald Trump’s senior trade adviser Peter Navarro Tuesday, calling him a “moron” on social media as the Tesla CEO further splits from the White House’s tariffs plan.

Musk’s remarks were in response to a CNBC interview with Navarro on that aired Monday, during which the White House trade adviser discussed how Tesla’s position as a “car assembler” rather than a car manufacturer could be at odds with Trump’s tariff policies. The comments come as Trump announced widespread tariffs on a swath of countries, causing market volatility and likely increasing the cost of cars by thousands of dollars.

“In many cases, if you go to his Texas plant, a good part of the engines that he gets, which in the EV case are the batteries, come from Japan and come from China. The electronics come from Taiwan,” Navarro said.

“The difference is, in our thinking and Elon’s on this, is that we want the tires made in Akron,” he continued. “We want the transmissions made in Indianapolis. We want the engines made in Flint and Saginaw. And we want the cars manufactured here.”

Musk said Navarro “is truly a moron” in an X post replying to a video of the comments being shared on the social media platform. “What he says here is demonstrably false,” he wrote, before calling Navarro “Peter Retarrdo” in another derogatory comment.

Musk claimed “Tesla has the most American-made cars,” in another series of X posts, adding that “Navarro is dumber than a sack of bricks.”

“By any definition whatsoever, Tesla is the most vertically integrated auto manufacturer in America with the highest percentage of US content. Navarro should ask the fake expert he invented, Ron Vara,” he added.

Tesla has dominated Cars.com’s American-Made Index since 2021, based on criteria including assembly location, where the parts are made, engine origin, transmission origin and US manufacturing workforce. Still, Tesla isn’t immune to tariffs, a reality that Musk has acknowledged.

“The tariff impact on Tesla is still significant,” he wrote on X last month.

Musk’s Tuesday remarks come after he posted, and then deleted, a comment saying Navarro’s PhD from Harvard is a “bad thing,” and that he hasn’t “built sh*t.”

Navarro dismissed concerns over a clash with Musk on Monday, saying “everything is good with Elon, no problem.” when speaking to CNBC.

Musk has also diverged with Trump on tariffs, posting videos about free trade and saying at an Italian event he believes there should be zero tariffs between the US and Europe. The Washington Post reported Monday that Musk also made a “direct appeal” to Trump.

It’s not the first time Musk has disagreed with Trump on a policy or personnel pick. But the split over tariffs is one of the more significant differences in perspective between the president and his biggest booster and top adviser.

The White House for its part, is shrugging off Musk’s comments.

“These are obviously two individuals who have very different views on trade and on tariffs. Boys will be boys and we will let their public sparring continue,” White House Press Secretary Karoline Leavitt said during a press briefing on Tuesday. “I think it also speaks to the president’s willingness to hear from all sides that he has people at the highest levels of this government, in this White House, who have very diverse opinions on very diverse issues.”