A key forecasting index for the U.S. economy fell an unexpected 0.1 percent in April, a private research organization reported on Thursday, signaling a possible stalling of the U.S. economy. The Conference Board said its index of leading indicators fell to 138.9 in April after rising to 139 the previous month. April's decline came amid rising gasoline prices, lagging consumer confidence, and increasing interest rates. “This latest decline, combined with some earlier softening, suggests growth in the third quarter may be slower,” Conference Board economist Ken Goldstein said in a statement. “With the price of a barrel of oil still around $70 and with interest rates slowly rising, the economy isn't likely to be picking up steam.” Only three of the 10 indicators that comprise the leading index increased in April. One indicator was unchanged and six were negative. The index is closely watched because it predicts economic activity three to six months in the future. The Conference Board's index of coincident indicators, which measures current economic activity, rose 0.2 percent to 122.6. The index of lagging indicators, which reflects past performance, rose 0.3 percent to 122.8.