A bill that would mandate the sale within six months or see TikTok facing a ban was approved by a US congressional panel on Thursday.
Earlier, users of the app had received a notification urging them to act to “stop a TikTok shutdown.”
A congressional aide told the BBC their office had received dozens of calls.
One Congressman said he had been contacted by children over the matter
TikTok confirmed to the BBC it had sent a notification urging TikTokers to “call your representative now” to urge them to vote against the measure.
The bill is expected to go to a full House floor vote next week.
It has been proposed by a cross-party group of 20 lawmakers who form the Select Committee on the Chinese Communist Party.
It was approved unanimously 50-0 on Thursday by the Energy and Commerce Committee. The Senate would need to approve it before it became law.
The committee chairwoman criticised TikTok’s mobilisation of its users, to which the platform responded: “Why are members of Congress complaining about hearing from their constituents? Respectfully, isn’t that their job?”
Media caption,The boss of TikTok was grilled at Congress last month on CCP ties
The bill pledges to “protect the national security of the United States from the threat posed by foreign adversary controlled applications”.
Lawmakers say TikTok’s owner ByteDance has links with the Chinese Communist Party – something denied by ByteDance and TikTok.
The bill makes specific reference to ByteDance – which would be forced under the terms of the bill to sell TikTok, or face removal from mobile app stores in the US.
It does not contain any provision for individual users of the app to face legal action.
“America’s foremost adversary has no business controlling a dominant media platform in the United States,” said committee chairman Mike Gallagher, a Republican of Wisconsin.
Raja Krishnamoorthi, an Illinois Democrat, said TikTok posed “critical threats to our national security” because its parent company was “required to collaborate” with China’s political leadership.
The bill’s proponents deny the move amounts to an overt ban on TikTok, arguing that ByteDance is being given a window of about six months to comply.
But in a statement posted to X, TikTok described the move as “an outright ban… no matter how much the authors try to disguise it”.
“This legislation will trample the First Amendment rights of 170 million Americans and deprive 5 million small businesses of a platform they rely on to grow and create jobs.”
The American Civil Liberties Union (ACLU) agreed, saying the move represented an effort to score “cheap political points during an election year”.
The ACLU further highlighted that many Americans relied on the app for information and communication.
The proposed legislation represents the latest attempt by American lawmakers to curb TikTok.
The app is banned on US government devices – although the re-election campaign of President Joe Biden has an account.
An attempt by former US President Donald Trump to ban TikTok and Chinese-owned WeChat hit legal obstacles and never came into force.