A federal judge scheduled a rare Sunday morning hearing to decide whether the U.S. can go through with its ban on the popular video-sharing app TikTok.

ByteDance Ltd., TikTok’s Chinese owner, has asked the court to block the ban, set to begin on Sunday night, even as it pursues approvals from the government for the sale of a stake in its U.S. operations to Oracle Corp. and Walmart Inc. under pressure from President Trump. It argued in court filings Friday that the ban would trample constitutional free-speech protections.

Trump cited national security risks in August, when he announced a ban on the widely used network from U.S. app stores. The president, who’s also barred WeChat, owned by China’s Tencent Holdings Ltd., has told ByteDance its only alternative is to sell its American TikTok business. The U.S. Justice Department argues the apps potentially give the China’s government access to millions of Americans’ personal data.

The government emphasized those concerns in a filing on Friday, urging U.S. District Judge Carl Nichols not to grant the temporary block. U.S. lawyers cited FBI Director Christopher Wray’s assessment that China poses the “greatest long-term threat to our nation’s information and intellectual property” as a reason for the ban.

“One of the tools that the PRC uses to further its goals is bulk data collection,” the U.S. government said, referring to the People’s Republic of China.

ByteDance, founded in 2012 by Zhang Yiming, has close ties to the Chinese Communist Party and must abide by laws that require it to cooperate with China’s government, the U.S. said.

“In April 2018, the CCP forced ByteDance to shutdown one of its other platforms, and Mr. Yiming issued a public apology in which he pledged to cooperate with and elevate official CCP media,” the U.S. said. “Following this public atonement, ByteDance underwent organizational restructuring with CCP infrastructure now built into it.”

The ban, announced in an Aug. 6 executive order, is part of a wider effort by the administration to take a hard line against Beijing, which Trump bets will help him win re-election. Starting at 11:59 p.m. on Sept. 27, it would remove TikTok from the app stores run by Apple and Google’s Android, the most widely used marketplaces for downloadable apps. People who don’t yet have the app wouldn’t be able to get it, and those who already have it wouldn’t have access to updates needed to ensure its safe and smooth operation. TikTok is used regularly by 19 million Americans.

Ahead of the looming deadline, ByteDance had argued for an expedited schedule in the case. The U.S. pushed back at a hearing on Thursday, saying ByteDance had filed a separate suit more than a month ago and was late in requesting the injunction in this one. In defense of the ban, the government again cited security concerns.

“TikTok is allowed to continue operating with respect to existing users but cannot add users, and the reason for that is that there are significant national security risks,” Assistant U.S. Attorney Daniel Schwei told the judge.

TikTok said that the ban was already undermining its business model by scaring users away, and that it had sought relief as soon as it was allowed to under the law. It said the government would have argued its request was premature if filed earlier.

“The urgency of this is created by the Sunday night ban,” attorney John Hall said. “That part of it makes absolutely no sense to us.”

Hall added the ban would increase risks to existing users by preventing them from getting regular security updates. The deadline also was affecting the company’s reputation with users, who are considering moving to less attractive platforms, the attorney noted.

In the social media industry, Hall said, “users retained is absolutely the lifeblood of their business.”

In Friday’s filing, TikTok’s lawyers argued that Trump is exceeding his authority with the proposed ban and acting in an “unreasonable and capricious manner” by seeking to cut off all transactions on the service.

The law being invoked “states the President’s authority does not extend to the direct or indirect regulation or prohibition of ‘personal communication’ and the international flow of ‘information or informational materials,’ such as film, photographs, and artwork, regardless of the ‘format or medium of transmission,”‘ the Chinese company’s lawyers argued.

Such a ban also would trample free-speech rights of U.S. users of the Chinese company’s platform, TikTok’s lawyers added. Millions of Americans “engage in core protected speech on TikTok in pursuit of a wide variety of political, social, and cultural ends,” according to the brief. “The Prohibitions unlawfully restrict this speech in violation of the First Amendment.”