Shares of technology companies fell as a rotation out of the sector continued.
After a seemingly unstoppable rise since March, "mega cap" tech stocks have fallen sharply this month, with the Nasdaq 100 on pace for its largest monthly decline since the financial crisis.
The speculation in tech stocks has been reminiscent of the late 90s, said one strategist.
"There was this cultlike fervor and again it was something akin to you couldn't fight it because the market kept going up," said Quincy Krosby, chief market strategist at Prudential Financial.
"And that fear of missing out ultimately grabbed most people because you wound up looking foolish as you watched people making so much money."
The Commerce Department ordered that U.S. downloads of TikTok and fellow Chinese app WeChat cease after Sunday night. WeChat also will be banned from processing payments and using U.S.-based web-hosting and content-delivery services at that point as well as from using its "constituent code" within the country's borders.
The orders followed efforts from Oracle and others to strike a deal to buy the U.S. operations of video-sharing app TikTok.
Write to Rob Curran at firstname.lastname@example.org