Reuters reported on Monday that Twitter Inc is preparing to agree to sell the company to billionaire Elon Musk for about $43 billion in cash, a price the Tesla CEO described as his "best and last" offer to the social media company.

The sources said Twitter may announce a deal worth $54.20 per share later on Monday once its board of directors meets to recommend the deal to Twitter shareholders.

The sources added that it is always possible for the deal to fall apart at the last minute.

Musk, the world's richest person according to Forbes statistics, is negotiating to buy Twitter in his personal capacity and Tesla is not involved in the deal.

Twitter shares were up 4.5% in premarket trading in New York on Monday at $51.15.

Musk said Twitter needs to get private to grow and become a true platform for free speech.

The deal will come just four days after Musk unveiled a financing package to support the acquisition.

This led Twitter's board of directors to take the deal more seriously and several shareholders to demand the company not allow the deal to slip away, Reuters reported on Sunday.