The offer from Musk, who has hinted at the possibility of a hostile bid, has prompted the social media company to adopt a “poison pill” to protect itself.

Musk, who is also the chief executive of electric-vehicle maker Tesla Inc, on Monday tweeted “Love Me Tender”, an Elvis Presley song, after Twitter opted for a plan to sell shares at a discount to prevent any attempt by shareholders to amass a stake of more than 15%. Musk currently has a 9.1% stake.

The New York Post on Tuesday reported Musk was willing to invest between $10 billion and $15 billion of his own money to take Twitter private, citing two sources familiar with the matter.

The billionaire, who is Twitter’s second-biggest shareholder, is planning to launch a tender offer in about 10 days and has tapped Morgan Stanley to raise another $10 billion in debt, according to the report.

Musk may also be willing to borrow against his current stake if necessary, a move that could possibly raise several billion additional dollars, according to the New York Post report.

Twitter declined to comment. Tesla did not immediately respond to a Reuters request for comment from Musk.

More private-equity firms have expressed interest in participating in a deal for Twitter, people familiar with the matter told Reuters on Monday without naming the firm.

The interest emerged after Thoma Bravo, a technology-focused private-equity firm, contacted the social media platform last week to explore a buyout that would challenge Musk’s offer.

Apollo Global Management Inc is considering ways it can provide financing to any deal and is open to working with Musk or any other bidder, the sources told Reuters.

Many investors, analysts and investment bankers expect Twitter’s board to reject Musk’s offer in the coming days, saying it is inadequate.