Stocks fall sharply after U.S. debt rating lowered

Stocks are falling sharply lower after Standard & Poor's dropped its outlook on U.S debt quality to negative.

The ratings service said it was making the move due to risks from the country's growing deficit. But the agency also reaffirmed the investment-grade credit ratings on country's long-term and short-term debt.

International concerns are also weighing on stocks even after several companies reported earnings that beat expectations. Traders are facing the renewed threat of a Greek debt default. China took another step to curb its runaway inflation.