U.S. stock index futures pointed to a lower open on Wall Street on Tuesday on mounting fears over corporate results, while a drop in oil prices is likely to weigh on energy stocks. * At 0940 GMT, futures for the S&P 500 SPc1 were down 0.54 percent, Dow Jones DJc1 futures were down 0.47 percent and Nasdaq 100 NDc1 futures were down 0.48 percent. * The beleaguered banking sector will remain in the spotlight after concerns about huge credit losses at Citigroup (C.N) dragged its stock 17 percent lower on Monday. * Sources familiar with the situation said on Tuesday Citigroup would close its private banking unit in China, which had sought to attract funds from the country's fast-growing ranks of millionaires, as it streamlines its businesses [ID:nHKG135978]. Citigroup shares in Frankfurt (TRV.F) were down 5.6 percent. * Kicking off the earnings season, aluminium producer Alcoa Inc (AA.N), which is slashing 15,000 jobs, posted a wider-than-expected quarterly loss after the closing bell on Monday, but revenue was $700 million higher than expected, and the company's stock was little changed after-hours. Alcoa shares in Frankfurt (ALU.F) slipped 0.7 percent. * In Tokyo, shares in Sony Corp (6758.T) tumbled 9 percent after a source with knowledge of the matter said the Japanese electronics and entertainment conglomerate would likely suffer an operating loss of about $1.1 billion due to sluggish sales and a stronger yen. Rival Toshiba Corp (6502.T) also dropped 9 percent after Japanese media said it, too, was headed for a big loss this financial year. * On the macro front, data showed on Tuesday that China's exports and imports both fell for a second consecutive month, underlining how badly the economy has been hit by the global financial crisis. * Shares in oil-sector companies will feel the pinch of lower crude prices CLc1, which fell nearly 3 percent to below $37 a barrel on mounting worries over global demand. * Economic indicators on Tuesday will include government reports on the U.S. trade balance and the federal budget, and a survey of sentiment among small-business owners, while companies set to report earnings include Linear Technology Corp (LLTC.O). * U.S. railroad CSX Corp (CSX.N) on Monday reported a lower preliminary fourth-quarter net profit that fell short of market expectations, citing a writedown related to its investment in The Greenbrier resort in West Virginia. * GSO Capital Partners LP, Blackstone Group's (BX.N) $25 billion credit hedge fund, is closing its Asia investment desk after failing to find attractive investments in the region, sources familiar with the matter said on Tuesday. * The Dow Jones industrial average .DJI fell 125.21 points on Monday, or 1.46 percent, to 8,473.97. The Standard & Poor's 500 Index .SPX dropped 20.09 points, or 2.26 percent, to 870.26. The Nasdaq Composite Index .IXIC lost 32.80 points, or 2.09 percent, to 1,538.79. (Reporting by Blaise Robinson, editing by Will Waterman)

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