Tesla chief Elon Musk mounted a hostile takeover bid for Twitter with an offer of $43 billion for the social media giant founded by billionaire Jack Dorsey.

"Twitter has extraordinary potential. I will unlock it," Musk said in a letter to Musk said in his letter to Twitter Chairman Bret Taylor on Wednesday, which was made public in a regulatory filing on Thursday.

Musk's offer price of $54.20 per share represents a 38% premium to Twitter's April 1 closing price, the last trading day before the Tesla CEO’s stake of more than 9% in the social media platform was made public.

Twitter's board said it would carefully review Musk's "unsolicited, non-binding" offer and decide on a course of action that was "in the best interest of the Company and all Twitter stockholders."

Musk said the "offer is my best and final offer" and he would reconsider his position as a shareholder if it was rejected.

Musk's latest to buy out Twitter comes just days after he turned down a seat on the board of the company following his acquisition of a 9.2 percent stake in the microblogging platform making him its biggest shareholder.

"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 said in his filing.

"However, since making my investment I now realize the company will neither thrive nor serve this societal imperative in its current form," he said.

Wedbush analysts said the Twitter board would likely be forced to accept the bid or seek another buyer.

Musk has more than 80 million followers since he joined Twitter in 2009 and has used it to make several announcements, including teasing a go-private deal for Tesla that landed him in trouble with regulators.

He has also been sued by former Twitter shareholders who claim they were deprived of the recent increase in its stock price because Musk waited too long to disclose his stake.