U.S. stocks were flat Tuesday morning, following downturns in Asia and Europe. A trade group in Washington said U.S. retailers struggled in the most recent week, with sales off 2.5 percent week-to-week. The International Council of Shopping Centers said, \"Customers appear to have taken a break as temperatures warmed up and gasoline prices continued to soar.\" Also in Washington, the National Association of Home Builders said its confidence index rose for the fifth consecutive month in September. In midmorning trading on Wall Street, the Dow Jones industrial average added 18.10 points, or 0.13 percent, to 13,571.20. The tech-heavy Nasdaq Composite index lost 0.95 points, or 0.02 percent, to 3,179.17. The Standard and Poor\'s 500 dropped 0.35 points, or 0.02 percent, to 1,460.84. The benchmark 10-year treasury rose 13/32 to yield 1.801 percent. The euro fell to $1.3067 from Monday\'s $1.3116. The U.S. dollar fell to 78.62 yen from 78.71 yen. In Tokyo, the Nikkei 225 index fell 0.39 percent, 35.62 points, to 9,123.77.