US President Joe Biden says Elon Musk’s relationships with foreign countries are “worthy of being looked at”.
Mr Biden was asked whether Mr Musk posed a national security threat and if Saudi Arabia helping him to buy Twitter should be investigated.
Saudi Arabia’s Prince Alwaleed bin Talal rolled over a $1.89bn (£1.7bn) Twitter stake into Mr Musk’s takeover.
This month the kingdom’s stake drew the attention of a Democratic senator, who called for a probe into the deal.
During a news conference at the White House on Wednesday a reporter asked Mr Biden: “Do you think Elon Musk is a threat to US national security and should the US, with the tools you have, investigate his joint acquisition of Twitter with foreign governments, which include the Saudis?”
“Elon Musk’s cooperation and/or technical relationships with other countries is worthy of being looked at,” Mr Biden said.
“Whether or not he is doing anything inappropriate — I’m not suggesting that. I’m suggesting it’s worth being looked at. That’s all I’ll say,” he added.
Mr Musk completed his $44bn takeover of Twitter last month putting an end to a prolonged legal battle. The deal was financed by Mr Musk and a group of other investors.
Saudi Arabia’s Prince Alwaleed and the Kingdom Holding Company are the second largest investor in the newly-private company, according to a filing with the US financial watchdog.
Earlier this month Democratic Senator Chris Murphy called for an immediate investigation into the national security implications of Saudi Arabia’s stake in Twitter.
“Given Twitter’s critical role in public communication, I am concerned by the potential influence of the Government of Saudi Arabia,” Mr Murphy, who leads a key Foreign Relations subcommittee, said in a letter.
Mr Musk has previously waded into contentious topics with comments about Ukraine and Taiwan.
Last month he denied a report that he had spoken to Russian President, Vladimir Putin before posting a Twitter poll with his suggestions for ending the war with Ukraine.
Ian Bremmer, the head of the Eurasia Group political risk consultancy, said that Mr Musk had personally told him about the conversation with Mr Putin.
“I have spoken to Putin only once and that was about 18 months ago. The subject matter was space,” Mr Musk tweeted.
Mr Musk has also weighed in on the highly contentious subject of China’s relationship with Taiwan.
In an interview with the Financial Times, the chief executive of Tesla said Taiwan should become a special administrative zone of China.
China’s ambassador to the US praised Mr Musk’s comments but his Taiwanese counterpart said freedom is “not for sale”.
Taiwan rules itself but Beijing claims it as part of its territory.