Citing threats to national security, a bipartisan group of lawmakers introduced a new bill Tuesday that would give China’s ByteDance six months to sell off TikTok or face a ban in the United States.

The new legislation could be the most significant threat yet to the wildly popular app.

"This is my message to TikTok: break up with the Chinese Communist Party or lose access to your American users," Rep. Mike Gallagher, the Republican chair of the House of Representatives' select China committee, said in a statement. “America’s foremost adversary has no business controlling a dominant media platform in the United States.”

Rep. Raja Krishnamoorthi, the top Democrat on the committee, said the bill addresses national security concerns posed by Chinese ownership of TikTok and protects American social media users from “the digital surveillance and influence operations of regimes that could weaponize their personal data against them.”

The bill would force TikTok to sever ties with its parent company ByteDance or be blocked by U.S.-based web hosting services and app stores. It has more than a dozen cosponsors including Rep. Elise Stefanik, a member of House Republican leadership. 

TikTok said the bill would give ByteDance a narrow timeline – 180 days – to find a buyer with the resources to buy TikTok and to overcome the technical challenges involved in spinning it off.

"This bill is an outright ban of TikTok, no matter how much the authors try to disguise it," TikTok said in an emailed statement. "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."

Dan Crenshaw, a Texas Republican, responded on social media platform X: "No one is trying to disguise anything. We want to ban TikTok. You’re correct."

TikTok denies it shares U.S. user data with the Chinese government.

TikTok has sought to reassure US officials, pointing to the $1.5 billion it has spent building an operation called Project Texas that walls off U.S. user data, but the system is porous, according to a Wall Street Journal report. 

The bipartisan bill, which would also give President Joe Biden the power to designate other apps as controlled by a “foreign adversary,” will be considered at an Energy and Commerce Committee hearing Thursday. Past legislative efforts have stalled. 

Jameel Jaffer, executive director of the Knight First Amendment Institute at Columbia University, said the bill raises First Amendment concerns.

"Congress can protect data privacy and security without banning Americans from accessing one of the world’s most popular communications platforms," Jaffer said in a statement. "It should start by passing a comprehensive privacy law restricting the kinds of information that TikTok and other platforms can collect. Banning Americans from accessing foreign media should be a last resort."

Scrutiny over TikTok’s relationship with Beijing put the company in the crosshairs during the Trump administration and the Biden administration. 

Last year, the Biden administration demanded that TikTok's Chinese owners sell their stakes or face a possible ban. It also supported Senate legislation that would have given the White House new powers to ban TikTok and other foreign-based apps that pose national security threats but the bill was never voted on.

Biden’s reelection campaign recently joined the app to appeal to younger voters. 

Former president Donald Trump tried to ban TikTok in 2020 but was blocked by the courts. 

In November, a federal judge blocked Montana's first-of-its kind state ban on TikTok, saying it violated the free speech rights of users.

TikTok is banned on government devices.