Biden the President Wants to Curb TikTok. Biden the Candidate Embraces Its Stars.

The White House is so concerned about the security risks of TikTok that federal workers are not allowed to use the app on their government phones. Top Biden administration officials have even helped craft legislation that could ban TikTok in the United States.

But those concerns were pushed aside on Thursday, the night of President Biden’s State of the Union address, when dozens of social media influencers — many of them TikTok stars — were invited to the White House for a watch party.

The crowd took selfies in the State Dining Room, drank bubbly with the first lady and waved to Mr. Biden from the White House balcony as he left to deliver his speech to Congress.

“Don’t jump, I need you!” Mr. Biden shouted to the young influencers filming from above, in a scene that was captured — naturally — in a TikTok video, which was beamed out to hundreds of thousands of people.

Thursday’s party at the White House was an example of Mr. Biden’s political concerns colliding head-on with his national security concerns. Despite growing fears that ByteDance, the Chinese parent company of TikTok, could infringe on the personal data of Americans or manipulate what they see, the president’s campaign is relying on the app to energize a frustrated bloc of young voters ahead of the 2024 election.

“From a national security perspective, the campaign joining TikTok was definitely not a good look — it was condoning the use of a platform that the administration and everyone in D.C. recognizes is a national problem,” said Lindsay Gorman, head of technology and geopolitics at the German Marshall Fund and a former tech adviser for the Biden administration.

TikTok is the second-most popular platform among U.S. teenagers behind YouTube, making it an alluring political tool. But concerns about the app’s structure have been growing, and a House committee advanced a bill this week that would keep TikTok out of U.S. app stores unless the platform broke from ByteDance.

When members of Congress talk about TikTok they tend to focus on the privacy concerns, and whether data about users is stored in China or accessible to Chinese officials who could demand the company turn over the information.

But national security officials have a deeper concern: The algorithms that guide what users see are now almost entirely designed in China. The key is to prevent Chinese engineers, perhaps under the influence of the state, from using the code in ways that could censor, or manipulate, what American users see. TikTok has pushed back on such concerns, saying that its opponents haven’t produced evidence to back those fears.

That is particularly important, officials say, as election season nears. If Chinese officials sought to influence the election, the app might provide a subtle way to do so. But even the legislation now wending through Congress might not affect that: It would not go into effect for more than five months after a bill is signed. At most, that would be just a month or so before Election Day.

The White House has been supportive of constraints.

Mr. Biden’s National Security Council called the bill in the House “an important and welcome step” and the White House press secretary, Karine Jean-Pierre, said it should move quickly to the president’s desk for his signature. While the legislation’s road in the Senate is unclear, Mr. Biden asserted on Friday that he approved of the package.

“If they pass it, I’ll sign it,” Mr. Biden said.

ByteDance has spent Mr. Biden’s tenure promoting a plan to eliminate security concerns about TikTok by storing its American user data on Oracle servers in the United States. That plan was at the heart of a 2022 draft agreement between ByteDance and administration negotiators. But senior administration officials had concerns at the time that the proposed agreement didn’t go far enough to address their concerns.

Despite all those worries, the political benefits of TikTok were clear this week.

Harry Sisson, a 21-year-old political commentator on TikTok, reached more than 800,000 followers from his perch at the White House on Thursday night as he and others watched Mr. Biden’s State of the Union address on Thursday.

“He directly called out the Supreme Court to their faces for overturning Roe v. Wade,” Mr. Sisson said in a post during the speech. “You gotta see this, take a look at the clip.”

Later, in his fourth video during the speech, Mr. Sisson said of the president: “He came over to talk to us about how content creation is super important in 2024 because, you know, the media landscape is changing.”

He added: “Like, nobody really watches cable news anymore.”

The Biden campaign declined to answer questions about the specific security protocols for its posting of TikToks or why the campaign embraced the platform before it has divested from ByteDance. The White House has denied that Mr. Biden’s national security team wants to ban the app.

“We don’t see this as banning these apps — that’s not what this is — but by ensuring that their ownership isn’t in the hands of those who may do us harm,” Ms. Jean-Pierre said on Wednesday. “This is about our national security, obviously, and this is what we’re focused on here.”

The Biden campaign joined TikTok on the night of the Super Bowl.

Previously, the administration had avoided opening its own TikTok accounts while tapping into the app’s audience by inviting social media stars to briefings on the Covid-19 vaccines and Russia’s invasion of Ukraine. But after declining the traditional halftime presidential interview on Super Bowl Sunday, the campaign arrived on TikTok with an inaugural post poking fun at a right-wing conspiracy theory claiming Mr. Biden had rigged the game.

Democrats say the embrace of social media platforms like TikTok is an attempt to meet voters where they are.

“We have to deal with the cards that we’ve been dealt,” said Quentin James, the co-founder of Collective PAC, an organization that aims to elect Black public officials. “If the tools are available we have to use it even though there are international security issues at play. If the Biden campaign were to lose access to this, leaving it to the Trump campaign and others to use it, it would be an extreme disadvantage.”

Former President Donald J. Trump attacked the administration for the potential ban of TikTok, saying it would only empower Meta, the parent company of Facebook.

Mr. Trump’s criticism of the effort was notable because while in office, he had worked on engineering a sale of TikTok’s operations in the United States to Oracle. Its chief executive, Safra Catz, was a member of Mr. Trump’s 2016 transition team and a major campaign supporter.

While the campaign tries to use the platform to connect with younger voters, the efforts by the White House and Congress to reform the company have infuriated TikTok users. After the House bill was introduced this week, TikTok took the unusually aggressive step of pushing a pop-up message to American users on Thursday that asked them to call their representatives and protest the bill. Some Capitol Hill offices said they were deluged by calls, including from teenagers. Lawmakers complained that TikTok had misrepresented the bill by claiming it specified an immediate ban on the platform.

Meanwhile, a video the Biden campaign posted about the North Carolina governor’s race quickly amassed comments asking Mr. Biden to stop a TikTok ban.

One user expressed confusion in a comment that attracted likes from others on the app: “Aren’t you about to ban TikTok? Why did your team even make you an account?”

David McCabe and David E. Sanger contributed reporting from Washington.