WASHINGTON (Reuters) - A group of 21 states and more than 50 U.S. lawmakers on Friday backed the Justice Department in its defense of a law that requires China-based ByteDance to sell TikTok's U.S. assets by Jan. 19 or face a ban.

"TikTok is a threat to national security and consumer privacy," said a court filing led by the state attorneys general of Montana and Virginia. "Allowing TikTok to operate in the United States without severing its ties to the Chinese Communist Party exposes Americans to the risk of the Chinese Communist Party accessing and exploiting their data."

A group of more than 50 lawmakers led by U.S. Representative John Moolenaar, a Michigan Republican and chair of the House select China committee and the panel's top Democrat Representative Raja Krishnamoorthi, said in a separate filing the law "provides a clear, achievable path for affected companies to resolve the pressing and non-hypothetical national security threats posed by their current ownership structures."

TikTok and parent company ByteDance and a group of TikTok creators have filed suits to block the law that could ban the app used by 170 million Americans.

The U.S. Court of Appeals for the District of Columbia will hold oral arguments on the legal challenge on Sept. 16, putting the fate of TikTok in the middle of the final weeks of the 2024 presidential election.

The congressional filing was signed by House Majority Leader Steve Scalise, a Republican, former House Speaker Nancy Pelosi, and Republican Senator Marco Rubio and Frank Pallone, top Democrat on the Energy and Commerce Committee. "Congress acted not to punish ByteDance, but to protect national security," the lawmakers wrote.

TikTok said "these filings ignore the fact that Congress passed the TikTok ban with no record supporting the government's claims. Moreover, these filings do nothing to change the fact that the Constitution is on our side as the TikTok ban would violate the First Amendment rights of 170 million Americans who use TikTok."

Driven by worries among U.S. lawmakers that China could access data on Americans or spy on them with the app, the measure was passed overwhelmingly in the U.S. Congress in April just weeks after being introduced.

The Justice Department last week asked a U.S. appeals court to reject legal challenges to the law saying "the serious national-security threat posed by TikTok is real."