U.S. stock index futures fell sharply on Monday as renewed fears of a Greek debt default prompted investors to book some of last week's gains and turn to safer assets such as gold.

European stock indexes fell 2 percent or more in morning trade, led by banking shares, including Deutsche Bank and Societe Generale , on worries euro zone leaders won't be able to prevent a default by debt-stricken Greece.

At meetings on Saturday, European Union finance ministers broke no new ground in dealing with the crisis and made no decision on whether to give more firepower to the 440 billion euro ($607 billion) bailout fund, as suggested by U.S. Treasury Secretary Timothy Geithner.

Investors' risk aversion also rose after the Greek prime minister, George Papandreou, canceled a visit to the United States to instead chair a cabinet meeting on Sunday, a day before EU and International Monetary Fund inspectors hold a conference call with Finance Minister Evangelos Venizelos to hear how Greece will plug this year's budget shortfall.

Stocks made some serious progress over the past five days. In fairness, though, equities still have a lot of ground to make up and there are significant technical sticking points just overhead, said Elizabeth Harrow, strategist at Schaeffer's Investment Research in Cincinnati, Ohio.

Uncertainty is still the prevailing theme on Wall Street.

A regional election defeat for German Chancellor Angela Merkel on Sunday, her sixth election defeat this year, also kept investors on edge.

S&P 500 futures lost 17 points and 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 were down 32.25 points, and Nasdaq 100 futures fell 142 points.

Spot gold was bid at $1,820.99 a troy ounce at 1101 GMT (7:01 a.m. EDT) from $1,810.73 late in New York on Friday. The precious metal hit a record high of $1,920.30 on September 6.

Wall Street rose for a fifth day in a row on Friday and the S&P 500 index scored its best week since early July.

Investors awaited U.S. President Barack Obama's deficit-reduction plan on Monday, ahead of the Federal Reserve's Federal Open Market Committee meeting later in the week.

Swiss bank UBS increased the amount it said it lost on unauthorized equity trades to $2.3 billion on Sunday and Chief Executive Oswald Gruebel said the alleged fraud would have consequences for strategy and possibly also for himself. U.S.-listed shares of UBS fell 0.9 percent to $11.77 in premarket trade.

Netflix Inc is separating its movie streaming business and its DVD-by-mail service, which will be called Qwikster, Chief Executive Reed Hastings said in a company blog post. The stock was down 1.3 percent at $153.13 in premarket trade.

U.S. homebuilder sentiment probably remained stuck at historic lows in September, with the National Association of Home Builders/Wells Fargo Housing Market index expected to stay flat at 15, according to a Reuters poll of economists. The data is due at 10:00 a.m..

(Editing by Padraic Cassidy)