The price of bitcoin jumped about 4% Monday afternoon after Tesla CEO Elon Musk tweeted that he was having active discussions regarding the sustainability of the digital coin.

Bitcoin was trading around $38,074, according to Coindesk, when at about 3:42 p.m. ET Musk posted on Twitter: “Spoke with North American Bitcoin miners. They committed to publish current & planned renewable usage & to ask miners WW to do so. Potentially promising.”

Within minutes, the price had shot up to more than $39,500. Overall, the coin is up more than 17% in the last 24 hours.

Microstrategy CEO Michael Saylor followed up on Musk’s tweet, saying he hosted a meeting between the Tesla CEO and some bitcoin miners that led to the formation of the Bitcoin Mining Council, which will promote sustainability.

Musk has been a big supporter of cryptocurrencies, helping rally the prices of digital coins, including bitcoin, several times in the past year. His tweets and comments around cryptocurrency often send the prices soaring or plunging.

In an SEC filing in February, Tesla revealed that it bought $1.5 billion worth of bitcoin and would accept it as a form of payment. The company later said it registered a net gain of $101 million from sales of bitcoin during the quarter, helping to boost its net profits to a record high in the first quarter.

However, his relationship with the digital coin changed earlier this month. He tweeted on May 12 that the company “suspended vehicle purchases” using bitcoin, out of concern over “rapidly increasing use of fossil fuels” for bitcoin mining. 

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