FBI Director Christopher Wray reiterated the bureau’s longstanding national security concerns about Chinese-owned video app TikTok to lawmakers today and said the agency is sharing its views with officials who are weighing a deal that would allow it to keep operating in the US.

Wray told lawmakers China’s government could use the app to control millions of users’ data or software, and its recommendation algorithm — which determines which videos users will see next — “could be used for influence operations if they so choose.”

“Under Chinese law, Chinese companies are required to essentially — and I’m going to shorthand here — basically do whatever the Chinese government wants them to do in terms of sharing information or serving as a tool of the Chinese government,” Wray told the House Homeland Security Committee. “That’s plenty of reason by itself to be extremely concerned.”

The Federal Bureau of Investigation has passed along its concerns to the Committee on Foreign Investment in the United States, the government body that’s reviewing the deal.

“As Director Wray specified in his remarks, the FBI’s input is being considered as part of our ongoing negotiations with the US Government,” said TikTok spokeswoman Brooke Oberwetter. “While we can’t comment on the specifics of those confidential discussions, we are confident that we are on a path to fully satisfy all reasonable US national security concerns.”

The popular video-streaming app, which has millions of users in the US, has emerged at the center of a long-running national security debate. At the same time, it’s become key to reaching young voters, who are increasingly eschewing social networks such as Facebook and Twitter.

The Biden administration is weighing a proposal to allow TikTok to continue to operate in the US under the ownership of Chinese parent ByteDance Ltd. The arrangement would include routing US user traffic through servers maintained by Oracle Corp., with the US-based database giant auditing the app’s algorithms.

However the effort has stalled over concerns the app would remain a threat, with China hawks on the Hill expected to criticize any agreement that stops short of an outright ban, or the sale of the platform to a US company. Congress is weighing legislation that would officially ban TikTok from all government phones.

Two influential Republican lawmakers wrote in a Washington Post column last week that TikTok should be banned outright in the US. Florida Senator Marco Rubio, vice chairman of the Senate Intelligence Committee, and Representative Mike Gallagher of Wisconsin said they planned to introduce legislation to ban the platform along with others “that are effectively controlled by the CCP.”

Wray offered to give lawmakers a classified briefing about the FBI’s concerns about the platform and the potential deal. He said the bureau’s foreign investment unit is providing input on the potential deal through the Cfius process and that he expects its concerns will be taken into account in any agreement.

The Justice Department, which oversees counter-intelligence operations in the US, has long harbored concerns about the app. The department’s No. 2 official, Deputy Attorney General Lisa Monaco, has expressed concerns in private that the agreement designed by the Biden administration doesn’t go far enough to keep the data of US users safe from Chinese actors, Bloomberg has reported.

Wray said the FBI is concerned about the threat specifically from the Chinese government, saying its laws are used as “an aggressive weapon” against US and Chinese companies “to do whatever the Chinese government wants them to do.”