People in the US will be banned from downloading TikTok from this Sunday.
The US commerce department said that starting 20 September, Americans will not be able to get the popular video-sharing app.
The ban will also cover the messaging app WeChat.
Chinese messaging app WeChat is also covered by the ban
President Donald Trump could still withdraw the ban before Sunday evening – if a deal is done between TikTok‘s Chinese owners ByteDance and US technology giant Oracle.
The two firms are in talks to create a new company, TikTok Global, that aims to address the White House’s concerns about the security of its users’ data, with Oracle having moved ahead of Microsoft in the race for a deal.
TikTok has 100 million users in the US.
A statement from the department said: “The Chinese Communist Party (CCP) has demonstrated the means and motives to use these apps to threaten the national security, foreign policy, and the economy of the US.
“Today’s announced prohibitions, when combined, protect users in the US by eliminating access to these applications and significantly reducing their functionality.”
It went on: “While the threats posed by WeChat and TikTok are not identical, they are similar. Each collects vast swaths of data from users, including network activity, location data, and browsing and search histories.
“Each is an active participant in China’s civil-military fusion and is subject to mandatory cooperation with the intelligence services of the CCP.
“This combination results in the use of WeChat and TikTok creating unacceptable risks to our national security.”
Trump: ‘I don’t mind’ if Microsoft buys TikTok
TikTok has said it would never share user information with Chinese authorities.
Bytedance and Oracle have submitted a proposal for a deal in which TikTok would become a separate US company with with an American board.
There would also be a security committee – the head of which would need government security clearance.
Microsoft had previously been in the running to take over the app, but their offer was rejected on 13 September.
Any deal will need the approval of both Washington and Beijing.