WASHINGTON (Reuters) - The Trump administration is expected to again extend a September 17 deadline for China's ByteDance to divest the U.S. assets of short-video app TikTok or shut it down, a source familiar with the matter told Reuters.

It would be the fourth reprieve granted by President Donald Trump from federal enforcement of a law that originally gave ByteDance until January 2025 to sell or shut down the popular social media platform.

Last month, Trump said he had U.S. buyers lined up for the app and could further extend the deadline. But he was equivocal on Sunday when asked about the app's future.

"I may or may not, we're negotiating TikTok right now. We may let it die, or we may, I don't know, it depends, up to China," Trump told reporters. "It doesn't matter too much. I'd like to do it for the kids."

The White House did not immediately respond to a request for comment on the expected extension, which, if granted, would suggest a reluctance to shut down an app used by 170 million Americans.

While China hawks in Washington have long feared Beijing could harness TikTok to spy on, blackmail or censor Americans, Trump has said he wants to save the app.

Progress on a deal has been slow, with any sharing of TikTok's prized algorithm with a U.S. buyer requiring approval from Beijing.

A deal had been in the works in the spring. It would have spun off TikTok's U.S. operations into a new U.S.-based firm, majority-owned and operated by U.S. investors, but was put on hold after China indicated it would not approve it following Trump's announcements of steep tariffs on Chinese goods.

U.S. Treasury Secretary Scott Bessent and U.S. Trade Representative Jamieson Greer began trade talks with Chinese Vice Premier He Lifeng and China's top trade negotiator, Li Chenggang, in Spain on Sunday that will touch on TikTok, but a deal is not expected before September 17, the source said.

TikTok was not discussed in previous rounds of U.S.-China trade talks in Geneva, London and Stockholm. The source said TikTok's public inclusion as an agenda item when the Treasury announced the latest talks gives the Trump administration political cover for another extension, which may annoy both Republicans and Democrats in Congress who mandated TikTok's sale.

Trump began his second term as president on January 20 and opted not to enforce the law requiring TikTok's U.S. asset sale or shut down. He first extended the deadline to early April, then from May to June, and a third time to September.