Twitter shares rose sharply Monday amid reports the company will soon accept Elon Musk's takeover offer, a dramatic shift after the board originally organized a "poison pill" defense to ward off the billionaire entrepreneur's hostile buyout bid.

The deal, which media outlets including The Wall Street Journal reported could be announced later in the day, would put the Tesla boss in charge of the influential social media site that is perhaps best known for at one time being the platform of choice for former US president Donald Trump.

About 20 minutes into trading, Twitter shares were up 3.6 percent amid an otherwise downbeat day in New York, where the Dow, Nasdaq and S&P 500 were all in the red by under one percent.

Musk had earlier this month launched his $43 billion hostile takeover bid for the company, casting it as a promotion of freedom of speech.

While the firm's board said it was reviewing the offer, it later rebuffed him and adopted a "poison pill" plan that would make it harder for Musk to acquire a controling stake.

Last week, Musk -- considered the world's richest man due to the explosive popularity of Tesla electric vehicles as well as other ventures -- said he had lined up $46.5 billion in financing for the deal and was "exploring" a direct tender offer to shareholders.

In a filing, Musk pointed to a $13 billion debt facility from a financing consortium led by Morgan Stanley, a separate $12.5 billion margin loan from the same bank, as well as $21 billion from Musk's personal fortune as being behind the deal.