US President Donald Trump has signed executive orders targeting TikTok and WeChat, two of China's biggest apps.
Under the orders, US firms must stop doing business with the companies within 45 days.
The move marks a major escalation in Washington's confrontation with Beijing over China's power in global technology.
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.
Earlier on Thursday, Washington announced recommendations that Chinese firms listed on US stock markets should be delisted unless they provided regulators with access to their audited accounts.