Elon Musk caused a stir on Wednesday by tweeting that he was buying Manchester United before saying several hours later that it was a joke.

It comes as the billionaire Tesla CEO faces a legal battle in the U.S. after backing out of a deal to buy Twitter for $44 billion. He is a prolific user of the platform, often musing about social issues or joking with his 103 million followers and occasionally getting into trouble with the U.S. regulators.

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Early Wednesday, Musk sent a tweet about his political affiliations and then added in a second tweet: "Also, I'm buying Manchester United ur welcome."

United's American owners, the Glazer family, have been strongly criticised by the club's fans for the team's underachievement in recent years.

Asked by a follower whether he was serious, Musk later tweeted: "No, this is a long-running joke on Twitter. I'm not buying any sports teams."

Musk previously ran afoul of the U.S. Securities and Exchange Commission for tweets claiming that he had the funding to take Tesla private in 2018, leading the electric vehicle maker's stock price to jump.

That led to a securities fraud settlement requiring that his tweets be approved by a Tesla attorney before being published.

He is now facing more legal woes over the deal to buy Twitter, which he negotiated in April.

Musk sold roughly $8.5bn worth of Tesla shares to help fund the purchase and lined up a diverse group of other investors to back him.

The deal fell apart last month after Musk said Twitter refused to provide him with enough information about the number of fake accounts on the platform.

Twitter could have tried to make him pay a $1bn breakup fee that he agreed to but instead is suing to force him to complete the purchase. The case is set to go to trial in Delaware in October.

United were arguably the biggest team in world football under manager Sir Alex Ferguson, winning 13 Premier League titles and two Champions League trophies.

But since Ferguson's retirement in 2013, the team have struggled to win trophies.

Last season, United finished 35 points behind champions Manchester City and there were protests against the Glazer family.

Many supporters in the club's huge international fanbase have opposed the Glazers since they took control in 2005, in part because they financed the takeover by putting the club in debt for the first time in decades.

The latest low came Saturday when United lost 4-0 to Brentford. It was United's second straight loss to open the season, leaving them bottom of the Premier League.

The Manchester United Supporters' Trust fan group, known as MUST, condemned the owners following last weekend's match.

"What we have witnessed tonight is an embarrassment -- no, a humiliation -- for Manchester United fans," the fan club said in a statement.

"And yet in many ways it was not a surprise. It feels like the culmination of a long-term direction of travel.

"MUST hold the owners of the Club primarily responsible for this new low in our decade of decline."