President Donald Trump has extended the deadline for TikTok's sale in the US for a further 90 days.

The video-sharing app has faced questions over its future after the US passed a law last year requiring the app to be banned unless sold by its Chinese parent company, ByteDance.

Lawmakers said it posed a risk to national security - something TikTok denies.

Trump, who vowed to save TikTok during his presidential campaign, signed an executive order on Thursday which has delayed the date for enforcing the law for a third time.

In a statement, TikTok said it was "grateful for President Trump's leadership and support" in keeping the app online for its 170m US users.

"We continue to work with Vice President Vance's Office," it added.

A deal for the sale of TikTok in the US by ByteDance must now be reached by 17 September, Trump said in a post on his platform Truth Social.

The further delay was an expected development in the long-running process of securing a buyer for TikTok.

It is thought the authorities in Beijing will need to approve any sale or part sale of the app by its parent company.

The law was prompted by fears in the US that TikTok or ByteDance could be forced to hand over data on US users by the Chinese government.

Trump said on Tuesday he expected there would be a further delay.

White House press secretary Karoline Leavitt said on Wednesday that a further 90-day extension would "ensure this deal is closed so that the American people can continue to use TikTok with the assurance that their data is safe and secure."

Trump tried to force a sale of TikTok to an American buyer in 2020, during his first term in office.

But last year, he signalled he'd had a change of heart, saying the platform had helped him win the 2024 presidential election.

"I have a warm spot in my heart for TikTok, because I won youth by 34 points," Trump said in December, although most young voters backed the Democratic candidate Kamala Harris.

The law was supposed to take effect on 19 January, a day before Trump's inauguration to a second term in office.

TikTok challenged its constitutionality in the courts. The Supreme Court upheld the law days before it was due to take effect.

Senate Select Committee on Intelligence Vice Chairman Mark Warner, a Democrat, criticized Trump's decision.

"Once again, the Trump administration is flouting the law and ignoring its own national security findings about the risks posed by a PRC-controlled TikTok," Warner said in a statement.

"An executive order can't sidestep the law, but that's exactly what the president is trying to do," Warner added.