SAN FRANCISCO — Billionaire Elon Musk has offered to buy Twitter for $41.39 billion, or nearly €38 billion, a regulatory filing showed on Thursday.

Musk's offer price of $54.20 per share represents a 38 percent premium to the closing price of Twitter's stock on April 1, the last trading day before his stake of more than 9 percent in the company was publicly announced.

“I invested in Twitter as I believe in its potential to be the platform for free speech around the globe, and I believe free speech is a societal imperative for a functioning democracy,” Musk wrote in a letter sent to Twitter Chairman Bret Taylor and disclosed in a securities filing.

“However, since making my investment I now realize the company will neither thrive nor serve this societal imperative in its current form. Twitter needs to be transformed as a private company,” he added.

Ever since his stake in Twitter was made public last week, the CEO of Tesla and SpaceX had been tweeting his ideas for the platform, including an "edit" feature that Twitter since confirmed it was working on.

The billionaire was initially set to take a seat on the company's board of directors, but Twitter CEO Parag Agrawal said on Monday that would not happen in the end.

A lawsuit has since been filed by Twitter shareholders in the United States alleging that Musk illegally delayed disclosing his stake in the social media company so he could buy more of the stock at lower prices. — Agencies