Stocks are slipping in midday trading following two days of gains.
Investors focused on problems in Ukraine and Iraq.
Continue Reading Below
Energy stocks fell more than the rest of the market, dragged down by a decline in the price of crude oil.
The Standard & Poor's 500 index fell four points, or 0.2 percent, to 1,932 as of midday Tuesday.
The Dow Jones industrial average lost 28 points, or 0.2 percent, to 16,541. Chevron and Exxon Mobil were among the biggest decliners in the Dow.
The Nasdaq composite fell 13 points, or 0.3 percent, to 4,388.
U.S. government bond prices were little changed. The yield on the 10-year Treasury note held steady at 2.43 percent.