NEW YORK, Dec. 8 (Xinhua) -- Wall Street lost ground on Tuesday, after credit-rating companies highlighted the risk of government deficits.

    Fitch Ratings cut Greece one step to BBB+ on Tuesday, the third-lowest investment grade, after S&P put Greece's A- rating on watch for a possible downgrade on Monday, signaling it may be reduced within two months.

    Meanwhile, Moody's Investors Service said deteriorating public finances in the U.S. and U.K. may "test the Aaa boundaries."

    Moody's Investors Service also cut its ratings on a raft of Dubai government-controlled companies, citing a lack of government support over the emirate's debt obligations.

    On corporate news, McDonald's tumbled most among Dow components after the fast-food giant said its global same-store sales rose 0.7 percent in November and its same-store sales fell 0.6 percent in the United States.

    The Dow Jones lost 76.94 to 10,313.17. Broader indexes also went lower. The Standard & Poor's 500 index dipped 7.27 to 1,095.98 and the Nasdaq lost 5.61 to 2,184.00.

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