TikTok and WeChat will be banned from US app stores from Sunday, unless President Donald Trump agrees to a last-minute deal.
The Department of Commerce said it would bar people in the US from downloading the messaging and video-sharing apps through any app store on any platform.
The Trump administration says the companies threaten national security and could pass user data to China.
But China and both companies deny this.
While the US government says this is a matter of national security, TikTok claims the proposed ban is motivated by politics.
If a planned partnership between Oracle and TikTok owner ByteDance is agreed and approved by President Trump, the app would not be banned.
It is not yet clear whether Mr Trump will approve the deal, but he is expected to review it before the Sunday deadline.
In a statement, the US Department of Commerce Secretary Wilbur Ross said: “At the president’s direction, we have taken significant action to combat China’s malicious collection of American citizens’ personal data.”
The department acknowledged that the threats posed by WeChat and TikTok were not identical but said that each collected “vast swathes of data from users, including network activity, location data, and browsing and search histories”.
ByteDance has denied that it holds any user data in China, saying it is stored in the US and in Singapore. Tencent, which owns WeChat, has said that messages on its app are private.
While TikTok has millions of users in the US, it is not clear how many of WeChat’s billion users are based outside China, although it is likely to be a significant number.