* Spanish, Italian yields rise on euro zone concerns
* New Greek election poll shows leftist Syriza has taken lead
* European Commission calls for banking union
* Research in Motion tumbles in premarket
* Futures off: Dow 95 pts, S&P 12.2 pts, Nasdaq 18.5 pts
By Chuck Mikolajczak
NEW YORK, May 30 (Reuters) - U.S. stock index futures dropped on Wednesday, as rising bond yields for Italy and Spain indicated worsening fears about a spiraling of the euro zone's debt crisis.
Further weighing on futures was the latest poll from Greece which showed the radical leftist SYRIZA party has taken the lead over the pro-bailout conservatives ahead of a national parliamentary election next month that may determine whether the debt-laden country stays in the euro zone.
Yields on 10-year Spanish bonds moved closer to the 7 percent level, a point at which other nations in the bloc were forced to seek a bailout.
Spain is expected to issue new bonds shortly in an effort to fund its troubled banks despite the increased borrowing costs.
Adding to the concern, Italian 10-year yields topped 6 percent for the first time since January at a bond sale, raising concerns the region is vulnerable to a contagion.
"The biggest drag we have on our markets right now is the concern over what is going to happen in Spain if they can't get some liquidity into their banking system," said Art Hogan, managing director of Lazard Capital Markets in New York.
"You are getting precariously close to a point where the government can't afford to fund themselves if they have to pay those kind of rates - there is going to have to be some sort of intervention here and it's just a function of when."
The region's fiscal woes sent the euro to its lowest level in 23 months against the dollar. U.S. equities have been closely tethered to the currency's fortunes, with a 50-day correlation between the euro and the S&P 500 index at 0.91.
Futures briefly cut losses and the euro bounced after the European Commission said the the euro zone should move toward a banking union, consider eurobonds and the direct recapitalization of banks from its permanent bailout fund as well as boost growth and cut debt.
S&P 500 futures fell 12.2 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 dropped 95 points, and Nasdaq 100 futures lost 18.5 points.
Economic data expected includes pending home sales for April. Economists in a Reuters survey expect a 0.1 percent rise compared with a 4.1 percent rise in the previous month.
Research In Motion Ltd dropped 7.4 percent to $10.40 in premarket trade as the company hired bankers for a far-reaching strategic review and to look for partnerships as the BlackBerry-maker warned it would likely report a shock fiscal first-quarter operating loss.
Apple Inc Chief Executive Tim Cook said technology for televisions was of "intense interest" but stressed the company's efforts would unfold gradually amid speculation the iPad and iPhone maker was on the brink of unveiling a revolutionary iTV.
Footwear retailer Finish Line Inc raised its profit estimate for the first quarter as it now sees sales better than it had initially thought.
Pep Boys-Manny, Moe & Jack plunged 19.8 percent to $8.90 in premarket after the automotive parts and service chain said the sale of the company to private equity firm Gores Group has been called off.
European shares headed for a third straight month of losses on concern over Spain's struggling banks and the country's rising borrowing costs, but the FTSEurofirst 300 index of top European shares pared losses losses after the EU Commission comments.
Asian shares slipped on fears about Spain while signs emerged that China may take a cautious stance on economic stimulus.