President Donald Trump’s executive order banning China’s TikTok could prevent U.S. app stores from offering the popular short-video app and make advertising on the platform illegal, according to a White House document seen by Reuters.

Trump signed an order last week prohibiting transactions with TikTok if its parent ByteDance does not reach a deal to divest it in 45 days. It did not specify the scope of the ban, stating only that the U.S. Department of Commerce would define which transactions would be barred at the end of the 45-day period.

The White House document, sent out to supporters last week, provides insight into the Trump administration’s thinking. It shows the U.S. government is considering disrupting key aspects of TikTok’s operations and funding, amid concerns over the safety of personal data that the app handles.

“Prohibited transactions may include, for example, agreements to make the TikTok app available on app stores ... purchasing advertising on TikTok, and accepting terms of service to download the TikTok app onto a user device,” the document states.

A source familiar with the White House document verified its authenticity. TikTok did not immediately respond to a request for comment.

Some technology industry experts said eliminating TikTok’s ability to be offered on Apple Inc (AAPL.O) and Google owner Alphabet Inc’s (GOOGL.O) app stores, which in turn allow it to be downloaded on iPhone and Android smartphones, could cripple the app’s growth.

“That kills TikTok in the U.S,” said James Lewis, a cyber security expert with the Washington-based Center for Strategic and International Studies. “If they want to grow, these rules are a huge obstacle.”

He added, though, that the U.S. government may not be able to prevent Americans from downloading TikTok from foreign websites.

Apple and Alphabet did not immediately respond to requests for comment.

Following Trump’s executive order last week, TikTok told advertisers it would continue to honor planned ad campaigns, refund any that it cannot fulfill, and work with major influencers to migrate to other platforms in the event of a ban. Some advertisers told Reuters they were drafting contingency plans and considering other apps for their marketing.

It is not clear whether Trump’s order will be implemented. Microsoft Corp (MSFT.O) has been leading negotiations to acquire the North America, Australia and New Zealand operations of TikTok under the supervision of the Trump administration. A successful deal would make banning transactions with TikTok moot.

The White House document seen by Reuters is not clear on whether the United States would implement a similar crackdown on WeChat, the social media app owned by China’s Tencent Holdings Ltd (0700.HK) that Trump also sought to ban in an executive order on last week.

TikTok, which has said is exploring legal challenges to Trump’s order, has 100 million active users in the United States, and is especially popular with teenagers. It has said U.S. user data is safely stored in the United States and Singapore, and that it would not hand over such information to the Chinese government.