Twitter announced on Monday it has accepted Tesla CEO Elon Musk's offer to acquire the company at 54.20 U.S. dollars a share, valuing the social media platform at 44 billion dollars.

"The Twitter Board conducted a thoughtful and comprehensive process to assess Elon's proposal with a deliberate focus on value, certainty, and financing," Twitter's Independent Board Chair Bret Taylor said.

"The proposed transaction will deliver a substantial cash premium, and we believe it is the best path forward for Twitter's stockholders," he added.

The company said that the transaction was unanimously approved by the board, and it might likely close this year following shareholder and regulatory approval and "the satisfaction of other customary closing conditions," adding that It's not a done deal until the matters are resolved.

Musk repeated his refrain that "free speech" is key to Twitter's future. "I hope that even my worst critics remain on Twitter because that is what free speech means," he tweeted.

"Free speech is the bedrock of a functioning democracy, and Twitter is the digital town square where matters vital to the future of humanity are debated," Musk noted in Twitter's statement announcing the deal.

"I also want to make Twitter better than ever by enhancing the product with new features, making the algorithms open source to increase trust, defeating the spam bots, and authenticating all humans. Twitter has tremendous potential - I look forward to working with the company and the community of users to unlock it," he added.