Wall Street opens lower as Janet Yellen speech awaited

U S stocks opened lower on Tuesday as investors awaited Federal Reserve Chair Janet Yellen's speech and oil prices skidded nearly 3%.

The Dow Jones industrial average was down 22.53 points, or 0.13%, at 17,512.86, the S&P 500 2.04 points, or 0.1%, at 2,035.01 and the Nasdaq Composite 10.83 points, or 0.23%, at 4755.96.