WASHINGTON (AFP, REUTERS, BLOOMBERG) - TikTok must either be sold or blocked in the US due to national security concerns, Treasury Secretary Steven Mnuchin said on Sunday (Aug 2) in the latest ominous US warning to the Chinese-owned app.

TikTok, he said, simply "cannot exist as it does."

Mnuchin did not comment directly on President Donald Trump's threat on Friday (July 31) to bar the wildly popular video-sharing app.

The secretary recalled that the Committee on Foreign Investment in the United States - which he chairs - is reviewing TikTok, which is especially popular with young audiences who create and watch its short-form videos and has an estimated one billion users worldwide.

But in one of many fronts in US-Chinese relations that have turned practically poisonous these days, US officials have said it could be a tool for Chinese intelligence.

TikTok denies any such suggestion.

"I will say publicly that the entire committee agrees that TikTok cannot stay in the current format because it risks sending back information on 100 million Americans," Mnuchin said Sunday on ABC.

In separate remarks on Sunday, Secretary of State Mike Pompeo said President Trump will take action shortly.

Chinese software companies doing business in the US are feeding data directly to Chinese authorities "whether it's TikTok or WeChat - there are countless more," Pompeo said on Fox News Channel's "Sunday Morning Futures".

Trump "will take action in the coming days with respect to a broad array of national-security risks that are presented by software connected to the Chinese Communist Party," Pompeo said.

"We're closing in on a solution and I think you'll see the president's announcement shortly," he added.

Mnuchin said he has spoken to leaders of Congress including House Speaker Nancy Pelosi and the top Democrat in the Senate, Chuck Schumer about what to do with TikTok's operations in the US.

"We agree there needs to be a change. Force a sale or block the app. Everybody agrees it can't exist as it does," Mnuchin said.

The Wall Street Journal reported Saturday that negotiations for Microsoft to buy the US operations of TikTok, owned by Chinese internet giant ByteDance, are on hold after Trump threatened to bar the app.

TikTok defended itself on Saturday, with its general manager for the US, Vanessa Pappas, telling users that the company was working to give them "the safest app," amid US concerns over data security.

"We're not planning on going anywhere," Pappas said in a message released on the app.

Reuters reported that ByteDance has agreed to divest the US operations of TikTok completely, two people familiar with the matter said on Saturday.

ByteDance's concession will test whether Trump's threat to ban TikTok is a negotiating tactic, or whether he is intent on cracking down on a social media app that boasts it has 100 million users in the United States.

Trump told reporters onboard Air Force One late on Friday that he would issue an order for TikTok to be banned in the United States. "Not the deal that you have been hearing about, that they are going to buy and sell... We are not an M&A (mergers and acquisitions) country," Trump said.

ByteDance was previously seeking to keep a minority stake in the US business of TikTok, which the White House had rejected.

ByteDance was valued at as much as US$140 billion (S$192.3 billion) earlier this year when one of its shareholders, Cheetah Mobile, sold a small stake in a private deal, Reuters has reported. The startup's investors include Japan's SoftBank Group Corp.

The bulk of ByteDance's revenue comes from advertising on apps under its Chinese operations including Douyin - a Chinese version of TikTok - and news aggregator app Jinri Toutiao, as well as video-streaming app Xigua and Pipixia, an app for jokes and humorous videos.