Trump inauguration live updates: Donald Trump moves swiftly to implement his new agenda

Amid a back-and-forth on the future of TikTok in the U.S., Trump signaled that he thinks the U.S. should own "half" of the social media app.

He said to stay in operation in the U.S., TikTok would need to relinquish 50% of its earnings to the U.S. -- Trump did not detail how this deal would work, but said it would be a "joint venture."

The president said he changed his mind about the social media app after using it, but noted he's worried about its impacts on children.

"Because I got to use it," he said about his 180 on TikTok. "And remember, TikTok is largely about kids. Young kids. If China is gonna get information about young kids, I don't know -- to be honest with you, I think we have bigger problems than that."

Trump said that if China does not approve of the 50% sale, it would be considered a "hostile act."

While signing a slew of executive orders from the Oval Office on Monday night, Trump found a letter that outgoing President Joe Biden had left for him inside the Resolute desk.

Trump found it after Fox News' Peter Doocy asked if he'd been left a letter from Biden.

After joking about reading it aloud to the press, Trump said he would read it privately first.

Click here for a look at the tradition of presidents leaving letters for their successors.

Among executive orders signed by Trump at the Oval Office is one ending birthright citizenship.

Such a move, though, is expected to face significant legal hurdles. Under the 14th Amendment to the Constitution, any person born within the territory of the U.S. is a U.S. citizen.

When a reporter pointed out that that order will likely be challenged, Trump said, "You could be right."

"We have good grounds," he added.

Trump, surrounded by executive orders he planned to sign Monday evening, also signed an order pardoning approximately 1,500 Jan. 6 rioters.

The order also includes six commutations, he said.

"We hope they come out tonight. Frankly, they're expecting it," Trump told reporters.

As of early January, more than 1,580 individuals have been charged criminally in federal court in connection with Jan. 6, with over 1,000 pleading guilty, according to the Department of Justice.

Click here for a closer look at the sweeping pardons and commutations.