"If it turns out to be an accurate report, and ultimately Flynn implicates Trump as having colluded with Russia to rig the election, obviously that creates a lot of turmoil," said Randy Frederick, vice president of trading and derivatives for brokerage Charles Schwab.
"But it's too early to say."
Stock movements in recent days have mirrored the news out of Washington, with a surprise endorsement for the tax plan from Republican Senator John McCain helping the Dow break above the 24,000 mark for the first time on Thursday.
At 11:28 am ET (1628 GMT), the Dow Jones Industrial Average was down 223.55 points, or 0.92 percent, at 24,048.8.