U.S. stock index futures were flat on Tuesday as investors looked ahead to a round of corporate results that could show the impact of overseas crises

on U.S. profits.

* Markets have been driven by uncertainty over Japan's nuclear power crisis and the civil unrest in the Middle East and North Africa. Wall Street ended slightly lower on Monday, recording the year's lowest volume, as investors worried the developments would be a headwind for stocks in the quarterly earnings season.

* Late Monday, Halliburton Co said it would cut its first-quarter earnings because of conflicts in the oil-producing region and weather-related events in North America and Australia.

* Companies expected to report earnings include Apollo Group , Lennar Corp and McCormick & Company Inc .

* Dow component Home Depot Inc late Monday said it would buy back $1 billion of outstanding shares through an accelerate stock buyback program with Barclays.

* Economic indicators include January Case-Shiller data, due at 9 a.m. and March consumer confidence, which is seen falling from the prior month.

* S&P 500 futures rose 1.3 points but were below fair value, a formula that evaluates pricing by taking into account interest rates, dividends and time to expiration on the contract. Dow Jones industrial average futures added 23 points and Nasdaq 100 futures rose 5.25 points.

* 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.

* Goldman Sachs downgraded Dow component Travelers Cos Inc to sell but affirmed its neutral view on the property and casualty insurance sector.

* On Monday, U.S. stocks fell, with consumer shares hurt after hotel operator Marriott International said an important financial measure would come in at the low end of its previous outlook. Halliburton's comments also pressured the stock in extended-trading hours.

(Editing by Kenneth Barry)