US President Donald Trump said on Tuesday that he would be open to tech billionaire Elon Musk - the owner of social media platform X - buying Chinese-owned app TikTok.

"I would be if he wanted to buy it," Trump told reporters when asked if he was open to Musk, the world's richest man and the head of a budget-cutting initiative in the new administration, acquiring the video-sharing platform.

TikTok is facing down a US law that ordered the company to divest from its Chinese owner ByteDance or be banned in the United States.

In one of his first acts in office, Trump ordered a pause on enforcing the law that should have seen TikTok effectively made illegal in the country on Sunday, a day before he took office for a second term.

The executive order directed his attorney general to delay the implementation of the law for 75 days.

To save the company's US operations, Trump on Monday also floated the idea of a 50-50 partnership between "the United States" and its Chinese owner ByteDance, though he did not provide details on how this could be achieved.

Asked on Tuesday if his phone had TikTok, which is banned on US government devices, Trump said: "No, but... I think I'll get it right now."

TikTok briefly shut down in the United States late Saturday as the law's sale deadline approached, leaving millions of dismayed users barred from the app.

With the tacit co-operation of Oracle, its server provider, TikTok restored service in the United States on Sunday crediting Trump's commitment to save the app for making the reversal possible.

But even if existing users can still enjoy TikTok, Apple and Google have still not made the app available in their app stores, therefore denying downloads to new users as well as updates to those who have it.

Companies that violate the law, which remains officially in effect, face penalties of up to US$5,000 per user if the app is accessed.

Last week, a report that Chinese officials were considering selling the company's US operations to Musk's social media platform X was met with a firm denial from TikTok. (AFP)