Amazon has told employees to delete the popular video app TikTok from phones on which they use Amazon email, citing security risks from the China-owned app, according to reports  and posts by Twitter users who said they were Amazon employees.

The notice said employees must delete the app by Friday to keep mobile access to Amazon email. Workers would still be allowed to use TikTok from an Amazon laptop browser.

Amazon is the second-largest U.S. private employer after Walmart, with with more than 840,000 employees worldwide. Amazon did not immediately reply to requests for comment.

In an emailed statement, TikTok said that Amazon did not notify it before sending the email. "We still do not understand their concerns," it continued, adding that the company would welcome a dialogue to address Amazon's issues.

Chinese internet giant ByteDance owns TikTok, which is designed for users outside of China, as well as a Chinese version called Douyin. The app is popular with young people, including millions of American users, but is the subject of national security concerns.

TikTok has been trying to appease critics in the U.S. and distance itself from its Chinese roots, but finds itself caught in an increasingly sticky geopolitical web.

TikTok recently named a new CEO, t op Disney executive Kevin Mayer, which experts said could help it navigate U.S. regulators. And it is stopping operations in of Hong Kong because of a new Chinese national security law that led Facebook, Google and Twitter to also stop providing user data to Hong Kong authorities.

But a top Trump administration official said this week that the government remains concerned about the national-security threat to the app's millions of U.S. users. When Fox News TV host Laura Ingraham suggested that the U.S. ban Chinese social media apps, "especially TikTok," Secretary of State Mike Pompeo said that "We're certainly looking at it."

Pompeo said the Trump administration has "worked on this very issue for a long time," including its stance against Chinese telecom firms Huawei and ZTE. The government has tried to convince allies to root Huawei out of telecom networks, saying the company is a national-security threat, with mixed success; Trump has also said he was willing to use Huawei as a bargaining chip in trade talks. Huawei has denied that it enables spying for the Chinese government.

"With respect to Chinese apps on people's cell phones, I can assure you the United States will get this one right too," Pompeo said, and added that if users downloaded the app their private information would be "in the hands of the Chinese Communist Party."

A U.S. national-security agency has been reviewing  ByteDance's purchase of TikTok's precursor, Musical.ly, while U.S. military branches banned the app from government-issued phones. Meanwhile, privacy groups say TikTok has been violating  children's privacy, even after the Federal Trade Commission  fined the company in 2019 for collecting personal information from children without their parents' consent.

TikTok, like YouTube, relies on its users for the videos that populate its app. They are under a minute long, and many feature dancing and lip-syncing. TikTok has a reputation as a fun, goofy video destination, but it has racked up concerns ranging from censorship of videos, including those critical of the Chinese government, the threat of sharing user data with Chinese officials and violating kids' privacy.

Amazon is likely concerned about a Chinese-owned app's access to employee data, said Susan Ariel Aaronson, a professor at George Washington University and a data governance and national-security expert. China, according to the U.S. government, regularly steals U.S. intellectual property.

Part of Amazon's motivation with the ban may also be political, Aaronson said, since Amazon "doesn't want to alienate the Trump administration."

Amazon and its founder, Jeff Bezos, are frequent targets of President Donald Trump. Bezos personally owns The Washington Post, which Trump has referred to as "fake news" whenever it publishes unfavorable stories about him. Last year, Amazon sued the U.S. government, saying that Trump's "personal vendetta" against Amazon, Bezos and the Post, led it to lose a $10 billion cloud computing contract with the Pentagon to rival Microsoft. Meanwhile, federal regulators as well as Congress are pursuing antitrust investigations at Amazon as well as other tech giants.

TikTok has content-moderation policies, like any social network, but says its moderation team for the U.S. is led out of California and it doesn't censor videos based on topics sensitive to China and would not, even if the Chinese government asked it to. As for sharing U.S. user data with the Chinese government, the company says it stores U.S. user data in the U.S. and Singapore, not China; that its data centers are outside of China; and it would not give the government access to U.S. user data even if asked.

Concerns about China are not limited to the U.S. India this month banned dozens of Chinese apps, including TikTok, because of tensions between the countries. India cited privacy concerns that threatened India's sovereignty and security for the ban. India is one of TikTok's largest markets and had previously briefly banned the app in 2019 because of worries about children and sexual content.

Amazon's move on TikTok may foretell actions by other companies. "If we are concerned about TikTok, we should be concerned about thousands of other apps that collect, sell, and give access to our location data, contacts, and photos on our phones," said Kirsten Martin, a professor of technology ethics at the University of Notre Dame. "I would also expect other companies to take a closer look as to what apps are allowed on their employees' phones."

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AP Business Writer Joseph Pisani contributed to this report.