The S&P 500 hit its lowest since August 2017 and the Dow hit its lowest since October 2017, while the Nasdaq sank to a 15-month low, toying with bear market territory for the second day in a row.

Adding to nerves was President Donald Trump saying there was a very good chance a government funding bill, which included funding for a wall along Mexico border, would not pass the Senate.

At 12:59 p.m. ET, the S&P 500 was down 24.51 points, or 0.99 percent, at 2,442.91. The index had risen as much as 1.5 percent at its session high.

The Dow Jones Industrial Average was down 159.72 points, or 0.70 percent, at 22,699.88 and the Nasdaq Composite was down 132.14 points, or 2.02 percent, at 6,396.26.