Major U.S. stock indexes reversed direction to turn lower in morning trading on Thursday as more doubts emerged over whether European leaders could reach a deal on further strengthening the region's rescue fund.

The Dow Jones industrial average <.DJI> lost 57.63 points, or 0.50 percent, to 11,446.99. The S&P 500 <.SPX> fell 6.04 points, or 0.50 percent, to 1,203.84. The Nasdaq Composite <.IXIC> dropped 29.76 points, or 1.14 percent, to 2,574.28.

A high-profile EU summit will go ahead on Sunday as planned, according to sources in Germany's ruling coalition, but it will not reach a decision on leveraging the euro zone rescue fund.

(Editing by Kenneth Barry)