US STOCKS-Wall St flat on global caution before quarter-end

* Trading volume low as positive quarter nears end

* Home Depot rallies on stock buyback program

* Case-Shiller shows home prices fell for seventh month

* Dow up 0.1 pct, S&P down 0.1 pct, Nasdaq up 0.2 pct

* For up-to-the-minute market news see [STXNEWS/US] (Updates to early morning)

By Ryan Vlastelica

NEW YORK, March 29 (Reuters) - U.S. stocks were little changed in choppy trading on Tuesday as continuing global crises kept investors cautious before the quarter's end.

The S&P 500 index has risen 4.2 percent in the first quarter as of Monday. Still, investors were reluctant to risk gains with Japan's nuclear power problems and the civil unrest in the Middle East and North Africa unresolved. Monday's trading volume was the lowest of the year.

"The quarter is ending with a lot of uncertainties out there, resulting in messy intraday moves at the same time that nothing is really happening," said Michael Shaoul, chairman of the New York-based Marketfield Asset Management, which oversees $973 million.

"There's nothing obvious about what investors need to do in this environment, and that's why you're seeing such low volume," he said. "No one has any reason to recommit capital."

After the market opened data showed U.S. consumer confidence fell in March as expectations about jobs and income growth worsened, according to a private sector group. For details, see [ID:N29279392]

Home Depot Inc late on Monday said it would buy back $1 billion of outstanding shares through an accelerated program. Shares rose 2.2 percent to $37.47 and were the top percentage gainers on the Dow. [ID:nN28219743]

U.S. single-family home prices fell for the seventh straight month in January, according to the S&P/Case-Shiller composite index of 20 metropolitan areas. However, the drop was not as much as expected. [ID:nDZE7DS003]

The Dow Jones industrial average <.DJI> was up 5.56 points, or 0.05 percent, at 12,203.44. The Standard & Poor's 500 Index <.SPX> was down 0.86 point, or 0.07 percent, at 1,309.33. The Nasdaq Composite Index <.IXIC> was up 6.04 points, or 0.22 percent, at 2,736.72.

Apollo Group fell 6.5 percent to $39.59 after the education company said new enrollment fell 45 percent in second quarter. [ID:nL3E7ET1V1]

Lennar Corp fell 1.3 percent to $19.49 after swinging to a first-quarter profit but reporting a drop in revenue. [ID:nN29249040]

Wal-Mart Stores will urge the U.S. Supreme Court on Tuesday to reject a case brought on behalf of female employees who allege the retailer gave women less pay and fewer promotions in the largest, class-action sex-discrimination lawsuit ever. Shares of the Dow component were 0.2 percent higher. [ID:nN28284791]

(Editing by Kenneth Barry)