The billionaire sold 1.2 million shares held by his trust for more than $1.2 billion on Friday, the latest in a flurry of his stock transactions, according to a U.S. securities filing released later in the day.

The world's richest person and Tesla's top shareholder last Saturday tweeted that he would sell 10% of his shares if users of the social media platform approved the move. The 10% would be about 17 million shares at the time of his tweet.

He has sold 6.36 million shares this week - around 37% of 17 million. He now needs to offload about 10 million more shares to fulfill his pledge to sell 10% of his holdings.

Shares of Tesla Inc closed lower on Friday, down 2.8% at $1,033.42, snapping an 11-week winning streak. The shares are up more than 46% this year following a sharp rally in October.

The stock sales, which marked the first time that Musk cashed out on a stake of that size since the company was founded in 2003, were massive by capital market standards, eclipsing the initial public offerings of most companies.

By getting Twitter users to green-light the move, he has blunted potential criticism of cashing out at a time when Tesla's valuation has become frothy and shares are at record highs.

Tesla shares fell 15.4% this week and lost some $187 billion in market value, more than the combined market capitalizations of Ford Motor Co and General Motors Co.

Despite the week's losses, Tesla is still the most valuable automaker in the world. Recent strong gains in the stock have underscored demand for shares of electric vehicle (EV) makers.

After the blockbuster market debut of Rivian Automotive Inc on Wednesday, the two most valuable U.S. automakers are EV companies.

In a veiled jab at the Irvine, California-based rival, Musk tweeted on Thursday: "There have been hundreds of automotive startups, both electric & combustion, but Tesla is (the) only American carmaker to reach high volume production & positive cash flow in past 100 years."

MORE SALES?

Musk had previously said he would have to exercise a large number of stock options this year, which would create a big tax bill. Selling some of his stock could free up funds to pay the taxes.

Prior to the sale, Musk owned a stake of about 23% in Tesla, including stock options. After his exercise on 2.15 million stocks on Monday, he has options for 20 million more shares he needs to exercise by next August.

"We expect the share sales will continue, as Musk holds millions of options worth billions of dollars that would otherwise expire worthless, and he has also prearranged share sales under 10b5-1 plans," said Jason Benowitz, senior portfolio manager at the Roosevelt Investment Group LLC in New York.