Amid a series of tweets Thursday, Musk - apparently frustrated by the Asian nation's import duties - compared China's trade policy to "competing in an Olympic race wearing lead shoes". "They've known it for years". A spokesman for Boring Co. didn't immediately respond to a request for comment.
Later on Thursday, Trump defied opposition from the Republican party and protests from global allies as he signed orders imposing stiff and sweeping new tariffs on imported steel (25 per cent) and aluminium (10 per cent). But Tesla's growth in the country has been slowed a couple main factors: that "tenfold [tariff] difference" Musk tweeted about, and Chinese laws requiring foreign automakers to partner with domestic companies.
Import duties and the difficulties Tesla has had avoiding them by trying to produce in China has held the company back in the world's biggest market for cleaner cars.
While the idea of creating a bold and new (underground) frontier for traffic jams always seemed a bit out there, Musk's latest iteration is equally a head scratcher. "To be clear, I think a fair outcome for all is quite likely". He said this on his Twitter page.
Tesla shares closed down 1 percent on Thursday and were off almost another percent in after-market trading.
He added that "when China or another country charges us 50 percent tariffs - more than that in some cases - and we charge them nothing, that's not fair".
The tweets came one day after Trump wrote that his administration had asked Beijing to cut the annual USA trade deficit by $100 billion (though his tweet mistakenly listed the amount at $1 billion). Those are problems for Tesla, which wants to expand its presence in China's growing electric vehicle market without compromising its independence or intellectual property.
"We raised this with the prior administration and nothing happened", Musk wrote, after tweeting at Trump about both the import duties and joint-venture ownership rules.
"For example, an American auto going to China pays 25% import duty, but a Chinese vehicle coming to the U.S. only pays 2.5%, a tenfold difference", the tweet read.
Musk has met with Trump on several occasions since his election in November 2016.
"That's from Elon, but everybody knows it", Trump said.
Musk, 46, was a member of Trump's advisory council before stepping down following the president's decision in June to pull the United States out of the Paris climate agreement.