TikTok went dark in the United States on Saturday night (local time), less than two hours before a ban was slated to go into effect. Visitors to the app were greeted with a message reading: "Sorry, TikTok isn't available right now. "A law banning TikTok has been enacted in the US. Unfortunately, that means you can't use TikTok for now." In Australia, users clicking on American-based users were also greeted with the message. TikTok was expected to go dark in the United States on Sunday (local time) after the Supreme Court upheld a ban on the Chinese-owned social media platform — but it could be back as early as Monday. Late on Saturday, TikTok began displaying a message reading: "We regret that a US law banning TikTok will take effect on January 19 and force us to make our services temporarily unavailable. "We're working to restore our service in the US as soon as possible, and we appreciate your support. Please stay tuned." The notice came just hours before the ban was set to go into effect. But how long the ban will last was in question after President-elect Donald Trump said he will "most likely" delay a ban on TikTok for 90 days after he takes office on Monday, adding that he has not made a final decision in a phone interview with NBC News on Saturday. "I think that would be, certainly, an option that we look at. The 90-day extension is something that will be most likely done, because it's appropriate. You know, it's appropriate. We have to look at it carefully. It's a very big situation," Trump said in the interview. "If I decide to do that, I'll probably announce it on Monday," he added. The warning from TikTok — and the suggestion of an extension — is the latest twist in a saga that's dragged on for months, leaving the fate of the app, with its 170 million US users, in limbo. The law blocking TikTok was passed last year with strong bipartisan support and signed into law by President Joe Biden. Lawmakers said TikTok's ties to China and its access to reams of data posed a threat to national security. Many US users told CNN they were bracing for an end to the app, including influencers and other small businesses that said they depended on the platform for a living. Still, they said, they held out hope the app would somehow be saved. But the Supreme Court on Friday upheld the ban, dashing hopes of a last-second judicial assist. Later on Friday, TikTok said it would go offline on Sunday unless there was intervention from the Biden administration. Some of the companies that operate app stores and run computer servers are said to be concerned that they will be held liable. If TikTok goes dark, it will be because those service providers stop carrying the app to avoid legal consequences. Meanwhile, Trump — who first warned of TikTok's dangers five years ago — is now casting himself as the app's saviour. Earlier this month, on his Truth Social account, he posted stats about his own popularity on TikTok and asked, "Why would I want to get rid of TikTok?" TikTok's CEO Shou Chew has met with Trump at his Mar-a-Lago home in the weeks leading up to the ban taking effect and is expected to attend Trump's inauguration on Monday. The law passed last year allows the president to delay the ban from going into effect by 90 days but requires evidence that parties working to arrange a sale of TikTok to a US-owned company have made significant progress. But TikTok's owner, ByteDance, has rejected would-be buyers. The company has cited its popularity among American users, and its value to small businesses across the country, as it fights to stay online without any change in ownership.