A possible sale of Chinese-owned TikTok's US operations to Microsoft is reportedly on hold after Donald Trump vowed to ban the video-sharing app.
A sale was thought close to agreement, but was put in doubt after the US president's warning on Friday, reports the BBC.
The Wall Street Journal said Microsoft had now paused talks despite TikTok owner ByteDance making last ditch efforts to win White House support.
It comes amid criticism of Trump's threat as an attack on free speech.
The popularity of the short-form video app has soared, with TikTok thought to have about half a billion active users worldwide - and about 80 million in the US - with a huge proportion of these in their teens or early 20s.
But some US politicians are worried the app's Chinese owner, Bytedance, poses a risk to national security because the app could be used to collect Americans' personal data. Regulators have also raised their own safety concerns.
Late on Friday, Trump told reporters aboard Air Force One: "As far as TikTok is concerned we're banning them from the United States."
And in a statement on Saturday, a White House spokesman said: "The administration has very serious national security concerns over TikTok. We continue to evaluate future policy."
The Wall Street Journal said Bytedance tried to make significant concessions to the White House, including creating of thousands of jobs over three years.
A sale of the US operation to Microsoft, which owns LinkedIn, would give the US tech giant a far greater presence in social media, an area dominated by rivals. The value of TikTok's US arm has been put at between $15bn and $30bn (£11bn-£23bn).
According to the Financial Times, some executives at ByteDance believe Trump's intervention may just be a negotiating ploy to help Microsoft secure a better deal.