Futures Off Highs as Bailout Enthusiasm Fades

U.S. stock index futures were higher Monday but off their best levels as questions began to formover whether Spain's bank aid would really help put an end to the debt crisis.

Futures initially surged over the weekend after euro zone finance ministers agreed on Saturday to lend Spain's banks up to $125 billion(100 billion euros) to shore up the region's ailing financial sector.

However, concerns lingered over Greece’s second round of elections on June 17, seen as a referendum on the debt-ridden nation's future in the euro zone. (Read More—Italy Well-Placed to Face Financial Turmoil: Minister)

"It is hard to argue that the move has not gone far enough with onlookers remaining cautious that Spain might ultimately need to go the whole hog for a full strings-attached bailout further along the horizon," said Andrew Wilkinson, chief economic strategist at Miller Tabak in New York.

Major financials were higher in pre-market trading including Bank of America, Citigroup and Morgan Stanley.

Last week, the three main U.S. share indexes logged this year’s biggest weekly gainson investor optimism that euro zone leaders would move to recapitalize Spain’s banks over the weekend. Facebook rallied above $27 a share, but still closed lower for the week.

Market sentiment was also boosted by better-than-expected economic data from China. The central bank reported Chinese banks made 793.2 billion yuan ($125 billion) worth of new loans in May, beating market expectations of 720 billion yuan. The data followed from Saturday’s news that year-on-year car sales in China rose 22.6 percent in May.

And in the U.S., several Federal Reserve regional presidents are scheduled to give speeches throughout the day, including Atlanta’s Dennis Lockhart, San Francisco’s John Williams and Cleveland’s Sandra Pianalto.

Apple’s annual Worldwide Developers Conference starts in San Francisco, with the company expected to unveil details of its new operating system, iOS6.

General Electric may be breaking off large parts of its lending business amid investor concerns that the conglomerate has become one of the largest banks in the U.S. GE is the minority shareholder of NBCUniversal.

Meanwhile, the International Air Transport Association said it expects Boeing's profit to decline $3 billion this year, down from $7.9 in 2011.

HMO stocks were among the biggest decliners after health insurer Centene said it will record a loss in the second quarter and slashed its 2012 earnings outlook. This comes after Molina Healthcare cut its full-year guidance last week. Rivals WellCare Health Plans , Coventry Health Care , and Amerigroup were all trading lower.

—By CNBC’s JeeYeon Park (Follow JeeYeon on Twitter: @JeeYeonParkCNBC)

Coming Up This Week:

MONDAY: Apple WWDC event, Atlanta Fed Pres Lockhart speaks, San Francisco Fed Pres Williams Speaks, Cleveland Fed Pres Pianalto Speaks
TUESDAY: NFIB small biz optimism index, import & export prices, Fed Gov. Tarullo speaks, 3-yr note auction, GM shareholders mtg
WEDNESDAY: Weekly mortgage apps, PPI, retail sales, business inventories, oil inventories, 10-yr note auction, OPEC mtg, Caterpillar shareholders mtg, Dimon testifies before Senate
THURSDAY: CPI, jobless claims, current account, 30-yr bond auction, AOL shareholders mtg; Earnings from Kroger, Smithfield Foods, Pier 1 Imports
FRIDAY: Empire state mfg survey, treasury int'l capital, industrial production, consumer sentiment, credit card default rates reported, quadruple witching

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