Trump said at a rally on Sunday ahead of his inauguration that the US will seek a joint venture to restore the short-video sharing app used by 170 million Americans.

TikTok issued an earlier statement after US users reported being able to access the Chinese-owned service's website while the far more widely used TikTok app itself began coming back online for some users with just a few basic services.

As of Sunday evening, the app remained unavailable for download on US app stores. TikTok stopped working for US users late on Saturday before a law shutting it down on national security grounds took effect on Sunday.

Trump said he would "extend the period of time before the law's prohibitions take effect, so that we can make a deal to protect our national security."