Stock index futures rose sharply on Tuesday, tracking global equities that gained after gauges of Chinese and euro zone economic activity came in less gloomy than feared.

Futures pointed to gains of more than 1 percent, a repeat of Monday's futures trade, though that rally fizzled and Wall Street closed only modestly higher, a sign of continued market volatility and investors' reluctance to buy.

While reads on China's factory sector and German business activity pointed to slowing growth, the slowdown wasn't as harsh as some had feared.

Investors also continue to look ahead to comments from Federal Reserve Chairman Ben Bernanke at an annual central bank conference in Jackson Hole, Wyoming, on Friday.

We're going to be range-bound until Friday, which is indicative of the manic state of investor psychology right now, said James Dailey, portfolio manager of TEAM Asset Strategy Fund in Harrisburg, Pennsylvania. There are swinging degrees of hope and despair with no news flow until we get some direction from a catalyst.

Some have speculated Bernanke could unveil fresh measures to revive the struggling economy, though he is most likely to outline gradual measures, which would disappoint those looking for something as dramatic as a fresh round of economic stimulus.

If there's no announcement, we could undercut the lows we saw earlier this month, Dailey said, though he added that the intensity of recent selling has been extraordinary and won't be sustainable.

S&P 500 futures rose 13.6 points and were above 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 149 points and Nasdaq 100 futures rose 27.5 points.

July U.S. new home sales, scheduled for release at 10:00 a.m., will give new insight into the state of the fragile housing sector. Sales are forecast at about 310,000 homes, roughly flat with June.

Banks will continue to be in focus after UBS AG said it plans to slash around 3,500 jobs in a cost-cutting measure. U.S.-listed shares of the lender rose 3.7 percent to $13.68 in premarket trading.

Goldman Sachs Group Chief Executive Lloyd Blankfein hired Reid Weingarten, a high-profile Washington defense attorney, a government source familiar with the matter said late on Monday. Investigations of Goldman and its role in the 2007-2009 financial crisis continue.

H.J. Heinz Co reported first-quarter earnings that fell from the prior year, though revenue was higher.

Omnicare Inc offered to buy smaller rival PharMerica Corp

for $441 million in cash, sending PharMerica shares up 37.5 percent in premarket. Omnicare rose 3.5 percent.

European stocks were up 1.4 percent, led by a rebound in cyclical shares such as industrials and miners, but volumes were thin as investors remained wary of another false start after last week's rebound from a 20-percent nosedive quickly disappeared.

U.S. stocks ended slightly higher on Monday after four weeks of losses as investors hesitated to take big risks without a catalyst for buying.

(Editing by Padraic Cassidy)

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