Tesla boss Elon Musk said early today he is "not sure" his takeover bid for social media firm Twitter will be successful.
He made the comment just hours after revealing that he had offered to buy the social media platform for £41.49 a share, or just over £30billion.
Twitter's Chief Executive Parag Agrawal said that Twitter was not being "held hostage" by the offer.
Speaking at a conference in Vancouver, Mr Musk said: "I am not sure that I will actually be able to acquire it."
He added that he had a Plan B if his bid for Twitter was rejected, but gave no further details of what that could mean.
Mr Musk also said that Twitter should be more open and transparent.
"I think it's very important for there to be an inclusive arena for free speech," he said.
The BBC says that, on Thursday, Mr Musk unveiled his offer to buy all the shares in Twitter that he does not already own.
In an official filing to US regulators, he said he was the right person to "unlock" the company's "extraordinary potential" and that, if his offer was not accepted, "I would need to reconsider my position as a shareholder".
Mr Musk also said that, if Twitter's board of directors chose to reject the offer, it would be "utterly indefensible not to put this offer to a shareholder vote".
Twitter confirmed that it had received the bid, but said its board must still review the "unsolicited, non-binding" offer, which values its shares at well below the level of more than £53 that they reached last summer.
Mr Musk already owns more than 9% of the social media platform.
He is the world's richest person, with a net worth of more than £200billion.
Mr Musk’s offer to buy Twitter has sparked concerns among Tesla investors and analysts that the electric car maker could suffer as the chief executive becomes distracted by his takeover play.
The idea of Mr Musk working to close a deal for Twitter, possibly by selling even more of his Tesla stake, and then him overseeing yet another company, has Tesla observers worried.
Gene Munster, managing partner at venture capital firm Loup Ventures, told Reuters: "Elon is distracted. He's got a lot of things going on. He's involved in a lot of different endeavours."
Shares in Tesla, the world's most valuable car maker, have fallen by more than 9% since he disclosed his large stake in Twitter last Monday. On Thursday, Tesla's stock dropped 3.7%.
While Mr Musk has talked about potential changes he would like to see Twitter make, Tesla faces its own challenges - the need to boost production at new assembly plants in Berlin and Texas, analysts said. Meanwhile, Tesla's Shanghai factory - its largest - has been idled by the Covid-19 crackdown in China.
Meanwhile, Brent crude futures were ahead 2.68% at $111.70 a barrel early this morning.
The UK’s top share index, the FTSE 100, was in front by 35 points at 7,616 when it finished trading yesterday.
The London Stock Exchange is closed today and also on Monday.