WASHINGTON (Reuters) - Peter Navarro, President Donald Trump's top trade adviser, on Monday dismissed tech-billionaire Elon Musk's push for "zero tariffs" between the United States and Europe, calling the Tesla CEO a "car assembler" reliant on parts from other countries.

Navarro, widely seen as the architect of Trump's tariff plans, told CNBC Musk had done a good job with his work to streamline government, but his comments on tariffs were not surprising given his role as "car person," the latest salvo in a growing feud between the Trump advisers.

"When it comes to tariffs and trade, we all understand in the White House - and the American people understand - that Elon is a car manufacturer, but he's not a car manufacturer. He's a car assembler," Navarro said, adding that many Tesla parts came from Japan, China and Taiwan.

"He's a car person. That's what he does, and he wants the cheap foreign parts."

Musk, speaking by video link at a congress of Italy's right-wing, co-ruling League Party just days after Trump announced hefty reciprocal tariffs against nearly 60 countries, said he hoped Europe and the United States agreed to "a zero tariff situation, effectively creating a free trade zone."

Trump's plans call for European Union countries to face a general tariff of 20%.

Tesla has seen its quarterly sales drop sharply amid a backlash against Musk's work with a new "Department of Government Efficiency." The company's shares are trading at $227.32 on Monday morning, about half their 52-week high.

U.S. share prices fell sharply again on Monday amid recession fears and concerns about the impact of Trump's sweeping tariffs. The S&P 500 index was down more than 20% from its all-time highs, putting the most closely followed benchmark for U.S. equities on track to confirm a bear market.

Navarro said he had not spoken with Musk since his post on X over the weekend suggesting Navarro's "PhD in Econ from Harvard is a bad thing, not a good thing," but said the two men would likely see each other at the White House on Monday, adding the personal comment was "no big deal."

He said the difference centered on Trump's push to reshore U.S. manufacturing, while Musk was reliant on foreign parts to manufacture Tesla vehicles in the United States.

"The difference is in our thinking and Elon's on this is that we want the tires made in Akron. We want the transmissions made in Indianapolis. We want the engines made in Flint and Saginaw, and we want the cars manufactured here," Navarro said.