* Consumer confidence drops vs expectations of gain
* Shorter week, 'window dressing' may add to volatility
* Dow, S&P off 1.2 pct, Nasdaq off 0.9 pct (Updates to mid morning)
By Edward Krudy
NEW YORK, June 30 (Reuters) - U.S. stocks fell on Tuesday after U.S. consumer confidence data showed a surprise drop in June, raising doubts about the speed on an economic recovery.
The Conference Board's U.S. consumer confidence index fell in June to 49.3, versus expectations of an increase, sparking investor concern about how quickly consumers will resume spending.
"Since we reached the early May highs, the markets have really been range-bound, with investors uncertain about the next direction for the market and also looking for the next catalyst that might have an impact on the market," said Michael Sheldon, chief market strategist at RDM Financial in Westport, Connecticut
The Dow Jones industrial average fell 99.15 points, or 1.16 percent, to 8,430.23. The Standard & Poor's 500 Index lost 10.84 points, or 1.17 percent, to 916.39. The Nasdaq Composite Index slipped 15.92 points, or 0.86 percent, to 1,828.14.
The S&P 500 is up 15.7 percent so far this quarter, putting it on track for its best period since the fourth quarter of 1998, when the index jumped nearly 21 percent.
On this last day of the quarter, fund managers are expected to enhance portfolios as part of "window dressing" by selling losing stocks and scooping up the winners. The process may add to volatility.
Analysts noted that a shortened trading week could also lead to increased volatility as well as thinner volumes. U.S. markets will be shut for the U.S. Independence Day holiday on Friday.
The S&P 500 has gained 36.3 percent since hitting a 12-year closing low on March 9 as early signs of an economic rebound surfaced.