According to sources familiar with the situation, Twitter Inc is likely to agree to a sale to Elon Musk for about $43 billion in cash, the sum the CEO of Tesla Inc has called his “best and last” bid for the social media business, reported Reuters.

According to the sources, Twitter may announce the $54.20-per-share agreement later on Monday after its board meets to endorse the transaction to Twitter shareholders. The sources however cautioned that the agreement could fall through at the last minute.

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According to Forbes, Musk, the world’s richest person, is negotiating to buy Twitter on his own, and Tesla is not participating in the deal.

The sources revealed that Twitter has not been able to acquire a ‘go-shop’ option in its agreement with Musk that would allow it to solicit alternative bids once the deal is completed. Nonetheless, Twitter would be permitted to accept an offer from a third party in exchange for paying Musk a break-up fee, according to the sources.

Reuters reported that because the issue is confidential, the sources requested anonymity. Requests from Reuters for a response from Twitter and Musk were not immediately returned.

Twitter’s stock was up 4.5 percent in pre-market trade in New York on Monday, closing at $51.15.

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Musk has stated that Twitter must be turned private in order to flourish and become a genuine forum for free speech.

The transaction would take place just four days after Musk outlined a financial plan to support the acquisition. This prompted Twitter’s board to examine the purchase more seriously, and many shareholders urged the firm not to let the possibility for a merger pass them by, according to Reuters on Sunday.

The sale would be an admission by Twitter that its new CEO, Parag Agrawal, who took over in November, is not making enough progress toward making the firm more profitable, despite the fact that the company is on schedule to reach lofty financial targets established for 2023. Even as late as November, Twitter’s stock was trading higher than Musk’s bid price.

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Musk’s bargaining strategy, which involves making a single offer and sticking to it, is similar to how another billionaire, Warren Buffett, negotiates purchases. Musk did not release any financial specifics when he first announced his bid for Twitter, which made the market suspicious of its prospects.