TikTok's decision comes weeks after US President Donald Trump signed an executive order giving Americans 45 days to stop doing business with video app's Chinese parent company, Bytedance.
TikTok will challenge in court a Trump administration crackdown on the popular Chinese-owned service, which Washington accuses of being a national security threat.
As tensions soar between the world's two biggest economies, US President Donald Trump has said TikTok could be used by China to track the locations of federal employees, build dossiers on people for blackmail, and conduct corporate espionage.
Trump signed an executive order on August 6 giving Americans 45 days to stop doing business with TikTok's Chinese parent company, Bytedance.
That is the order the video-sharing platform will target in its suit.
"To ensure that the rule of law is not discarded and that our company and users are treated fairly, we have no choice but to challenge the Executive Order through the judicial system," TikTok said in a statement on Saturday
TikTok has repeatedly denied being any threat to US security, and Beijing has called the Trump crackdown political manipulation.
US WeChat users sue Trump
Some US-based users of WeChat are suing Trump in a bid to block an executive order that they say would effectively bar access in the US to the hugely popular Chinese messaging app.
The complaint, filed on Friday in San Francisco, is being brought by the nonprofit US WeChat Users Alliance and several people who say they rely on the app for work, worship, and staying in touch with relatives in China. The plaintiffs said they are not affiliated with WeChat, nor its parent company, Tencent Holdings.
In the lawsuit, they asked a federal court judge to stop Trump's executive order from being enforced, claiming it would violate its US users' freedom of speech, free exercise of religion, and other constitutional rights.
“We think there's a First Amendment interest in providing continued access to that app and its functionality to the Chinese-American community,” Michael Bien, one of the plaintiffs' attorneys, said Saturday.
Trump's fight against Chinese firms
The twin executive orders, one for each app, are expected to take effect September 20, or 45 days from when they were issued. The orders call on Commerce Secretary Wilbur Ross, who is also named as a defendant in the US. WeChat Users Alliance lawsuit, to define the banned dealings by that time.
It remains unclear what the orders will mean for the apps’ millions of users in the US, but experts have said the orders appear intended to bar WeChat and TikTok from the app stores run by Apple and Google. That would make them more difficult to use in the US.
“The first thing we’re going to seek is a postponement of the implementation of the penalties and sanctions —- a reasonable period of time between explaining what the rules are and punishing people for not complying with them,” Bien said.
WeChat, which has more than 1 billion users, is less well-known than TikTok to Americans without a connection to China.
Mobile research firm Sensor Tower estimates about 19 million US downloads of the app. But it is a crucial infrastructure for Chinese students and residents in the US to connect with friends and family in China and for anyone who does business with China.
Within China, WeChat is censored and expected to adhere to content restrictions set by authorities. The Citizen Lab internet watchdog group in Toronto have said WeChat monitors files and images shared abroad to aid its censorship in China.
Even so, the US WeChat Users Alliance complaint argued that losing access to the app would harm millions of people in the US who rely on it, noting it is the only app with an interface designed for Chinese speakers.
“Since the executive order, numerous users, including plaintiffs, have scrambled to seek alternatives without success.
They are now afraid that by merely communicating with their families, they may violate the law and face sanctions," according to the complaint.