Stocks were poised for a lower open on Monday as political turmoil in Italy sparked worry the euro zone debt crisis could overwhelm the region's third largest economy.

Benchmark Italian government bond yields rose to their highest since 1997 at 6.67 percent. Many analysts said yields above 7 percent would make funding costs unsustainable for Italy's huge public debt, one of the highest in the world.

Italian Prime Minister Silvio Berlusconi, under pressure from markets and rebels in his party, fought to hang on to power and denied reports he would resign within hours. Party rebels threatened to bring down his government in a backlash over its failure to adopt reforms to defuse a debt crisis.

As soon as Greece looks like we can now sort of digest the risk right off the issues, in comes the 800-pound gorilla into the room. Italy is a much, much larger concern, with issues that have been lingering for decades, said Peter Kenny, managing director at Knight Capital in Jersey City, New Jersey.

This is not something you can cordon off. Italy is central to the European zone and it is going to force the European Union to recalibrate everything that has been taken for granted thus far in the conversation.

S&P 500 futures fell 2.7 points and were below fair value, a formula that evaluates pricing by taking into account interest rates, dividends and time to expiration of the contract. Dow Jones industrial average futures lost 21 points while Nasdaq 100 futures dropped 0.25 point.

A former deputy head of the European Central Bank was expected to emerge as Greek prime minister as political leaders negotiated over elements of a new coalition to push through a bailout.

With a light U.S. economic calendar this week and earnings season winding down, the euro zone debt crisis was expected to be front and center for investors this week.

Sysco Corp advanced 1.4 percent to $28.20 in premarket trading after it reported quarterly earnings.

Best Buy Co Inc edged down 0.8 percent to $27.10 premarket after the consumer electronics chain agreed to buy British partner Carphone Warehouse Group Plc for $1.3 billion and scrapped plans for a chain of European megastores.

Tekelec climbed 10.7 percent to $10.96 premarket after the network technology provider agreed to be bought by a private equity group for about $780 million in cash.

(Reporting by Chuck Mikolajczak; editing by Jeffrey Benkoe)