"I've been warning people about a correction...but pullbacks are still being viewed as buying opportunities," said Randy Frederick, managing director of active trading at derivatives at the Schwab Center for Financial Research. "I remain bullish overall for 2013, but we're still likely to see a pullback in the second quarter. Stay long the market, but continue to hedge on the downside."
(Read More: Global Concerns? Bet on Small Caps: Goldman Sachs)
Among earnings, Pfizer declined after the drugmaker reported quarterly results that fell short of Wall Street expectations, citing the stronger dollar and the spin-off of its animal health unit Zoetis. The company also lowered its full-year outlook.
U.S. Steel dipped after the steelmaker posted a quarterly loss as its sales fell more than 10 percent. And Cummins reported quarterly results that missed forecasts. Shares erased most of their earlier losses to close flat.
Pitney Bowes plunged to lead the S&P 500 laggards after the digital communication software maker posted disappointing earnings and also forecast full-year profit largely below estimates.
BP gained after the oil giant announced a sharp rise in earnings, with the sale of its Russian venture TNK-BP offsetting a fall in oil and gas production.
Major European banks including Deutsche Bank and UBS both posted better-than-expected first quarter profits. However,Anheuser-Busch InBev, the world's largest brewer, cut its outlook for full-year growth in its second-biggest market, Brazil, after earnings fell short of expectations.
Dreamworks Animation is scheduled to post earnings after the closing bell.
To date, a little over 60 percent of S&P 500 companies have posted quarterly results, with 69 percent of firms topping earnings expectations, according to the latest data from Thomson Reuters. If all remaining companies report earnings in line with estimates, earnings will be up 4 percent from last year's first quarter.
Meanwhile, only 44 percent companies have beaten revenue forecasts. On average, sales have come in 1 percent below estimates.