Futures Turn Mixed; Facebook Declines

U.S. stock index futures trimmed earlier gains to turn mixed in a volatile pre-market session, as investors awaited data on existing home sales and after Fitch cut Japan's credit rating.

Best Buy reported better-than-expected quarterly sales and earnings, while maintaining its outlookfor the year. However, shares of the retailer turned lower after staging a rally immediately after the announcement.

Facebook shares continued to decline in pre-market trading after tumbling almost 11 percent in the previous session. Meanwhile, Reuters reported that an analyst at Morgan Stanley, the lead underwriter for Facebook's IPO, cut his revenue forecastson the social networking giant just a few days before the trading debut.

Also weighing on futures, Fitch ratings agency downgraded Japan’s credit rating from triple A to double A+ with a negative outlook, on fears that the country’s public debt will reach 239 percent of its gross domestic product by the end of the year.

Japanese Finance Minister Jun Azumi reacted to the announcement by saying the government would make efforts to implement social welfare and tax reforms.

European shares staged a rally on hopes that euro zone leaders will reach some form of agreement on a policy response to the debt crisis when they meet in Brussels on Wednesday.

Meanwhile, the Organization for Economic Cooperation and Development (OECD) projected that global growth would ease to 3.4 percent this year from 3.6 percent in 2011. The group also showed support for Eurobonds—a policy that new French President Francis Hollande raised over the weekend.

The National Association of Realtors releases existing home sales for April data at 10 am ET. Economists polled by Reuters forecast a 4.6 million annualized unit total, compared with 4.48 million in March.

Dell and Take Two are scheduled to report earnings after the close.

In corporate news, Bayer and Onyx Pharmaceuticals failed to show in a late-stage clinical study that their blockbuster drug Nexavar can prolong the lives of patients with lung tumors, the largest target group in the cancer market.

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

Coming Up This Week:

TUESDAY: Existing home sales, 2-yr note auction, Atlanta Fed's Lockhart speaks, Arkansas/Kentucky Primaries; Earnings from Dell, Take Two
WEDNESDAY: Weekly mortgage apps, FHFA home price index, oil inventories, 5-yr note auction, Minneapolis Fed's Kocherlakota speaks, CME shareholders mtg, Kraft shareholders mtg; Earnings from Hewlett-Packard, Big Lots, Toll Brothers, NetApp, Pandora
THURSDAY: Durable goods orders, jobless claims, 7-yr note auction, BlackRock shareholders mtg, Goldman Sachs shareholders mtg, McDonald's shareholders mtg; Earnings from Costco, Tiffany
FRIDAY: Consumer sentiment, USDA food prices outlook

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