NEW YORK (CNNMoney) -- U.S. stocks could face another rocky session, as investors await the latest discussions on how to solve Europe's debt crisis.
Dow Jones industrial average (), S&P 500 ( ) and Nasdaq ( ) futures were all slightly lower. Stock futures indicate the possible direction of the markets when they open at 9:30 a.m. ET.
Attention will remain focused on Europe as the Spanish banking system teeters on the edge of collapse, and Greece comes closer to a possible exit from the euro.
Spain's Treasury Minister Cristobal Montoro told a Spanish radio network early Tuesday that the country was nearly shut out of global finance markets, and that its banking system would need help from other European countries. Yields on Spain's 10-year bond crept slightly higher to 6.4%.
Credit rating agency Standard & Poor's said Monday that there is a one-in-three chance Greece will leave the euro currency union in the coming months.
Finance officials of the world's seven largest economies, the G-7, are reportedly holding an emergency call Tuesday to discuss the crisis.
In the United States, economic data on tap includes the Institute for Supply Management's services index. But even positive news could be drowned out by other concerns, said David Kelly, chief global strategist for JPMorgan Funds.
"There is a general gloom that has enveloped markets," Kelly said. "The markets are more focused on Spain right now, but the greatest threat to eurozone is in the hands of the Greek voters. Until we get some clarity from (the June 17) Greek elections, we won't know what's going to happen."
Kelly said that he believes stocks have become oversold, as investors have moved out of riskier assets such as equities and into U.S. Treasuries in the last month. He said that stock values relative to bonds are at their cheapest point in the last 50 years.
The price on the benchmark 10-year U.S. Treasury was little changed Tuesday morning, leaving the yield near its 1.53% level late Monday.
"Are there concerns? Yes. Is it the gloomiest environment in the last 50 years? No," he said. "Those stretched valuations is making it hard for markets to fall significantly further.'
CNNMoney's Fear & Greed Index remained in extreme fear territory Tuesday.
U.S. stocks finished little changed after a choppy trading session Monday.
World markets: European stocks were mixed in afternoon trading. The DAX ( ) in Germany slid 0.8%, while France's CAC 40 ( ) edged up 0.7%. London's stock market is closed Tuesday in celebration of the Queen's Diamond Jubilee.
Asian markets ended on a higher note. The Shanghai Composite () ended up about 0.2%, while the Hang Seng ( ) in Hong Kong added 0.4% and Japan's Nikkei ( ) rose 1%.
Economy: The ISM's services index for May is due out at 10 a.m. ET. Economists surveyed by Briefing.com expect the index to fall slightly to 53.1 from April's 53.5. But any reading above 50 still indicated growth in the service sector, which makes up the majority of the U.S. economy.
Companies: Starbucks ( , Fortune 500) announced plans to buy a bakery chain after the market closed Monday. Preliminary news of an impending business initiative sent shares higher at the close, but the acquisition itself was not enough to keep investors' interest. Shares fell 2.2% in premarket trading.
Facebook (shares continue their slide early Tuesday, losing another 1% in premarket trading after a 3% drop on Monday. Reports Monday that Facebook is looking at ways to allow children younger than 13 to use the site is prompting new criticism of the social networking company.)
Oil for July delivery slid 25 cents to $83.73 a barrel.
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