TikTok is threatening legal action against the US after Donald Trump ordered firms to stop doing business with the Chinese app within 45 days.
The company said it was “shocked” by an executive order from the US President outlining the ban.
TikTok said it would “pursue all remedies available” to “ensure the rule of law is not discarded”.
Mr Trump issued a similar order against China’s WeChat in a major escalation in Washington’s stand-off with Beijing.
WeChat’s owner, Tencent, said: “We are reviewing the executive order to get a full understanding.”
The president has already threatened to ban TikTok in the US, citing national security concerns, and the company is now in talks to sell its American business to Microsoft. They have until 15 September to reach a deal – a deadline set by Mr Trump.
The executive orders against the short-video sharing platform TikTok and the messaging service WeChat are the latest measure in an increasingly broad Trump administration campaign against China.
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.
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What did Trump say?
In both executive orders, Mr Trump claims that the spread in the US of mobile apps developed and owned by Chinese firms “threaten the national security, foreign policy, and economy of the United States”.
Both orders say any unspecified “transactions” with the apps’ Chinese owners or their subsidiaries will be “prohibited”.
The orders cite legal authority from the National Emergencies Act and the International Emergency Economic Powers Act.
Mr Trump’s executive order claims TikTok’s data collection could allow China to track US government employees and gather personal information for blackmail, or to carry out corporate espionage.
He notes that reports indicate TikTok censors content deemed politically sensitive, such as protests in Hong Kong and Beijing’s treatment of the Uighurs, a Muslim minority.
The US president says the Department of Homeland Security, the Transportation Security Administration (which oversees US airport screening) and the US Armed Forces have already banned TikTok on government phones.