(AP) — Twitter’s board is negotiating with CEO Elon Musk over his bid to buy the social media platform and a deal could be announced as early as Monday, according to media reports.

Twitter and Musk negotiated into the early hours Monday over his bid to buy the social media platform, The New York Times reported, less than two weeks after the billionaire first revealed a massive stake.

Musk said last week that he had lined up $46.5 billion in financing to buy Twitter, putting pressure on the company’s board to negotiate a deal.

The Times, citing people with knowledge of the situation who it did not identify, said the two sides were discussing details including a timeline and fees if an agreement was signed and then fell apart. The people said the situation was fluid and fast-moving.

Shares of Twitter Inc. rose 4% at the opening bell.

Twitter had enacted an anti-takeover measure known as a poison pill that could make a takeover attempt prohibitively expensive. But the board decided to negotiate after Musk updated his proposal to show he had secured financing, according to The Wall Street Journal, which was first to report the negotiations were underway.

Also, a rival bidder to Musk may not be stepping up any time soon, fearful of the byzantine task of moderating content on the platform, something that Musk has vowed to do less of.

“The Twitter Board could not find a white knight and with Musk’s financing detailed the clock has essentially struck midnight for the board which is why negotiations have begun to get a deal done,” said Dan Ives, who follows Twitter for Wedbush Securities.

On April 14, Musk announced an offer to buy the social media platform for $54.20 per share, or about $43 billion, but did not say at the time how he would finance the acquisition.

Last week, he said in documents filed with U.S. securities regulators that the money would come from Morgan Stanley and other banks, some of it secured by his huge stake in the electric car maker.

Twitter has not commented.

Musk has said he wants to buy Twitter because he doesn’t feel it’s living up to its potential as a platform for free speech.

In recent weeks, he has voiced a number of proposed changes for the company, from relaxing its content restrictions — such as the rules that suspended former President Donald Trump’s account — to ridding the platform of its problems with fake and automated accounts.

Musk is the world’s wealthiest person, according to Forbes, with a nearly $279 billion fortune. But much of his money is tied up in Tesla stock — he owns about 17% of the company, according to FactSet, which is valued at more than $1 trillion — and SpaceX, his privately held space company. It’s unclear how much cash Musk has.