President Donald Trump has told US firms they have 45 days to stop doing business with TikTok and WeChat, claiming the Chinese apps are a threat to national security.
Mr Trump signed two executive orders targeting two of China's biggest apps.
The announcement comes as Microsoft is in talks to buy TikTok ahead of a 15 September deadline set by Mr Trump.
The executive orders against the short-video sharing platform TikTok - owned by Chinese firm ByteDance - and the messaging service WeChat - owned by the Tencent conglomerate is the latest measure in an increasingly broad Trump administration campaign against China.