(Reuters) -President Donald Trump signed an executive order on Monday delaying by 75 days the enforcement of a ban of popular short-video app TikTok that was slated to be shuttered on Jan. 19.

The short video service used by 170 million Americans was briefly taken offline for U.S. users on Saturday, hours before a law that said it must be sold by its Chinese owner ByteDance on national security grounds took effect on Sunday. U.S. officials had said that under ByteDance, there was a risk of Americans' data being misused.

TikTok restored access on Sunday and thanked Trump for providing assurances to TikTok and its business partners that they would not face hefty fines to keep the app running. The app and website were operational on Monday, but TikTok was still not available for download in the Apple and Google app stores, suggesting the two companies were waiting for clearer legal assurances.

Trump's order hours after he was inaugurated on Monday directs the attorney general to not enforce the law "to permit my administration an opportunity to determine the appropriate course of action with respect to TikTok."

The order directs the Justice Department to issue letters to companies like Apple, Alphabet's Google and Oracle that supply services to TikTok "stating that there has been no violation of the statute and that there is no liability for any conduct that occurred during the above-specified period."

The debate over TikTok comes at a tense moment in U.S.-China relations. Trump has said he intends to place tariffs on China but has also indicated he hopes to have more direct contact with China's leader. 

"Frankly, we have no choice. We have to save it," Trump said at a rally on Sunday ahead of his inauguration, adding that the U.S. will seek a joint venture to restore the app used by half of Americans.