The halt occurred at about 11:30 am Eastern time today.
The exchange said in a statement that it was experiencing a "technical issue" that it was working to resolve as quickly as possible.
Before trading was halted, US indexes were lower as investors worried about China's ability to stem a stock market slide.
The Dow Jones industrial average was down 215 points, or 1.2 per cent, to 17,561.
The Standard & Poor's 500 gave up 24 points, or 1.2 per cent, to 2,057. The Nasdaq was down 73 points, or 1.5 per cent, to 4,924.