The Chinese government could use TikTok to control the data of millions of American users, according to the FBI.
Addressing a US Senate hearing on Wednesday, FBI director Christopher Wray said the Chinese-owned video app "screams" of security concerns.
He told a Senate Intelligence Committee on worldwide threats to US security that China's government could use the social media platform to control software on millions of devices, as well as drive narratives to divide Americans over Taiwan or other issues.
Expressing concerns that China could feed misinformation to users, Mr Wray said: "Yes, and I would make the point on that last one, in particular, that we're not sure that we would see many of the outward signs of it happening if it was happening."
He added: "This is a tool that is ultimately within the control of the Chinese government - and it, to me, it screams out with national security concern."
It comes after the White House backed legislation introduced on Tuesday by a dozen senators to give President Biden's administration new powers to ban TikTok and other foreign-based technologies if they pose national security threats.
The endorsement has boosted the efforts by a number of politicians to ban the app, which is owned by Chinese company ByteDance and used by more than 100 million Americans.
Several other top US intelligence officials including director of National Intelligence Avril Haines, CIA director William Burns and National Security Agency director Paul Nakasone also agreed at the hearing that TikTok posed a threat to US national security.
On Tuesday, Mr Nakasone expressed concern during Senate testimony about TikTok's data collection and potential to facilitate broad influence operations.