US stocks opened lower on Friday, with S&P 500 Index sliding 5.63 points, or 0.49 percent, to trade at 1,190.71 at 09:50 a.m. EST. The Dow Jones Industrial Average is down 44.77 points, or 0.40 percent, to trade at 11,136.46. The Nasdaq Composite Index fell 0.44 percent to trade at 2,503.47.

Traders are cautious over China's move to raise reserve ratio by 0.5 percentage points from November 29 and developments regarding debt crisis in Ireland.

The sentiment is also likely weighed on a prepared speech by Fed Chairman Ben Bernanke, who has defended the latest $600 billion stimulus plan and remarks over currency undervaluation.

“The committee believes that the best way to continue to deliver the strong economic fundamentals that underpin the value of the dollar, as well as to support the global recovery, is through policies that lead to a resumption of robust growth in the context of price stability in the United States,” Bernanke said in a speech to be given at a European Central Bank conference in Frankfurt conference on Friday.

Currency undervaluation inhibits necessary macroeconomic adjustments.......large and persistent imbalances in current accounts represent a growing financial and economic risk, Bernanke said.

On the corporate front, Salesforce.com Inc. soared nearly 16 percent after it issued an upbeat fourth quarter revenue forecast. Shares of Intuit Inc. fell 6 percent after its second quarter earnings guidance missed expectations.

Del Monte Foods Co is up nearly 12 percent after private equity firm Kohlberg Kravis Roberts is in advanced talks to buy the food and pet products company, according to a Reuters report.

On the currency front, the euro strengthened 0.22 percent to 1.3673 against the dollar, while the greenback edged down 0.09 percent to 83.44 against the yen.

Crude oil futures pared earlier gains and lost 0.20 percent to $84.88/barrel and gold futures fell 0.73 percent.

European stock markets are currently trading down with U.K. FTSE 100 down by 63.03 points, German DAX30 edged down 13.80 points and French CAC 40 down by 25.69 points.