NEW YORK CITY, RAW – Billionaire entrepreneur Elon Musk took aim at Twitter Inc with a $43 billion ($A58 billion) cash takeover offer, with the Tesla CEO saying the social media company needs to be taken private to grow and become a platform for free speech.

“I think it’s very important for there to be an inclusive arena for free speech,” Musk said at a TED Talk in Vancouver when asked about why he made the bid.

Musk, already the San Francisco-based company’s second-largest shareholder, made the bid in a letter to Twitter’s board on Wednesday. The offer was made public in a regulatory filing on Thursday.

His offer price of $54.20 per share represents a 38 per cent premium to Twitter’s April 1 close, the last trading day before his 9.1 per cent stake in the social media platform was made public.

Investors were not immediately convinced. Shares of Twitter about were flat in afternoon trading. Some argued Musk’s bid undervalued the micro-blogging platform that has become a global means of communication for individuals and world leaders.

Saudi Arabia’s prince Alwaleed bin Talal tweeted from his verified account about the deal. Describing himself as one of the “largest & long-term shareholders of Twitter,” he said Musk’s offer undervalued the company and he rejected it.

Musk, for his part, told Twitter it was his “best and final offer” and said he would reconsider his investment if the board rejects it.

Twitter banned former President Donald Trump over concerns around incitement of violence following last year’s US Capitol attack by his supporters.

In an interview with Sirius XM’s Americano Media on Wednesday – before Musk’s announcement – Trump said he “probably wouldn’t have any interest” in returning Twitter, where he had more than 88 million followers.

White House spokesperson Karine Jean-Pierre declined to comment on Musk’s offer for Twitter, saying that market regulators operate independently from political leadership.

Company employees, some of whom were panicked over Musk’s impact on its ability to moderate content, were expected to attend a Twitter all-hands meeting later on Thursday to discuss the news, one source told Reuters.

Twitter will review the offer with advice from Goldman Sachs and Wilson Sonsini Goodrich & Rosati, a source told Reuters.

Twitter’s lower-than-expected user additions in recent months have raised doubts about its growth prospects, even as it pursues big projects such as audio chat rooms and newsletters.

“The big question for the Twitter board now is whether to accept a very generous offer for a business that has been a serial underperformer and tends to treat its users with indifference,” said Michael Hewson, chief market analyst at CMC Markets.

Twitter will not decide on the fate of Musk’s bid on Thursday, according to a source familiar with the situation.

What the board is discussing is the parameters of the valuation process and it would then ask its advisers to review the bid and await for the results, the source said.

The board was also reportedly considering a “poison pill” tactic to deter Musk from increasing his share.

In business, a “poison pill” refers to a defensive tactic that might discourage hostile takeovers.

For instance they could give existing shareholders the right to purchase additional shares at a discount, effectively diluting the ownership interest of a new, hostile party.