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.”
As well as WeChat, Tencent is also a leading gaming company and its investments include a 40% stake in Epic Games – the company behind the hugely popular Fortnite video game.
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 Trump administration claims that the Chinese government has access to user information gathered by TikTok, which the company has denied.
TikTok, which is owned by China’s ByteDance, said it had attempted to engage with the US government for nearly a year “in good faith”.
However, it said: “What we encountered instead was that the administration paid no attention to facts, dictated terms of an agreement without going through standard legal processes, and tried to insert itself into negotiations between private businesses.”
The executive orders against the short-video sharing platform and the messaging service WeChat are the latest measures 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.
China’s Foreign Ministry on Friday accused the US of using national security as a cover to exert hegemony.
What did Donald Trump say?
In both executive orders, Mr Trump says 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”.
The US government says TikTok and WeChat “capture vast swaths of information from its users”.
“This data collection threatens to allow the Chinese Communist Party access to Americans’ personal and proprietary information.”
The executive order also claims both apps gather data on Chinese nationals visiting the US, allowing Beijing “to keep tabs” on them.
Mr Trump’s executive order also says 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 China’s treatment of the Uighurs, a Muslim minority.
The orders have been issued under legal authority from the National Emergencies Act and the International Emergency Economic Powers Act.
What does TikTok say?
In its most robust response so far to the US government, TikTok says the executive order that has been issued is based on “unnamed reports with no citations”.
“We have made clear that TikTok has never shared user data with the Chinese government, nor censored content at its request,” it said.
“We even expressed our willingness to pursue a full sale of the US business to an American company.”
Mr Trump said this week he would support the sale to Microsoft as long as the US government received a “substantial portion” of the sale price.
TikTok said the new executive order “risks undermining global businesses’ trust in the United States’ commitment to the rule of law”, adding it sets “a dangerous precedent for the concept of free expression and open markets”.
“We will pursue all remedies available to us in order to ensure that the rule of law is not discarded and that our company and our users are treated fairly – if not by the administration, then by the US courts,” it said.