WASHINGTON, DC, United States (AP) — US lawmakers grilled the CEO of TikTok over data security and harmful content Thursday, responding sceptically during a tense committee hearing to his assurances that the hugely popular video-sharing app prioritises user safety and should not be banned.

Shou Zi Chew's rare public appearance came at a crucial time for the company, which has 150 million American users but is under increasing pressure from US officials. TikTok and its Chinese parent company, ByteDance, have been swept up in a wider geopolitical battle between Beijing and Washington over trade and technology.

In a bipartisan effort to reign in the power of a major social media platform, Republican and Democratic lawmakers pressed Chew on a host of topics, ranging from TikTok's content moderation practices, how the company plans to secure American data from Beijing, and its spying on journalists.

"Mr Chew, you are here because the American people need the truth about the threat TikTok poses to our national and personal security," Committee Chair Cathy McMorris Rodgers, a Republican, said in her opening statement.

Chew, a 40-year-old Singapore native, told the House Committee on Energy and Commerce that TikTok prioritises the safety of its young users and denied it's a national security risk. He reiterated the company's plan to protect US user data by storing it on servers maintained and owned by the software giant Oracle.

"Let me state this unequivocally: ByteDance is not an agent of China or any other country," Chew said.

TikTok has been dogged by claims that its Chinese ownership means user data could end up in the hands of the Chinese Government or that it could be used to promote narratives favourable to the country's Communist leaders.

In 2019, the Guardian reported that TikTok was instructing its moderators to censor videos that mention Tiananmen Square and images unfavorable to the Chinese Government. The platform says it has since changed its moderation practices.

ByteDance admitted in December that it fired four employees last summer who accessed data on two journalists and people connected to them while attempting to uncover the source of a leaked report about the company.

For its part, TikTok has been trying to distance itself from its Chinese origins, saying 60 per cent of ByteDance is owned by global institutional investors such as Carlyle Group.

"Ownership is not at the core of addressing these concerns," Chew said.

China has also said it would oppose any US attempts to force ByteDance to sell the app.

In one of the most dramatic moments, Republican Rep Kat Cammack played a TikTok video that showed a shooting gun with a caption that included the House committee holding the hearing, with the exact date before it was formally announced.

"You expect us to believe that you are capable of maintaining the data security, privacy and security of 150 million Americans where you can't even protect the people in this room," Cammack said.

TikTok spokesperson Ben Rathe said the company on Thursday removed the violent video aimed at the committee and banned the account that posted it.

Chew also noted the failure of US social media companies to address the very concerns for which TikTok was being criticised.

"American social companies don't have a good track record with data privacy and user security," he said. "Look at Facebook and Cambridge Analytica, just one example."

As the Energy and Commerce committee questioned Chew, Secretary of State Anthony Blinken was questioned about the threat TikTok poses at a separate committee hearing Thursday. Asked by Representative Ken Buck, a Republican of Colorado, if the platform is a security threat to the United States, Blinken said: "I believe it is."

"Shouldn't a threat to United States security be banned?" Buck responded.

"It should be ended one way or another. But there are different ways of doing that," Blinken responded.