Stocks set for a lower start on economic concerns

U.S. stocks are poised to start Tuesday's session lower after closing the previous session mostly with declines. On Monday, Federal Reserve Chairman Ben Bernanke said that rates won't rise soon, as the economic recovery still faces "formidable headwinds." FedEx (FDX) lifted its earnings guidance due to improved activity, but even this news failed to bolster sentiment as investors worry about the economy and employment picture.

More here: Before the bell: Futures decline despite FedEx lifting guidance