The S&P 500 fell for a fifth straight session in choppy trading on Tuesday, again testing key technical support ahead of the start of first quarter earnings season.
The Dow Jones Industrial Average fell 71.48 points, or 0.55%, to 12,858.11. The Standard & Poor's 500 Index lost 6.64 points, or 0.48%, to 1,375.56. The Nasdaq Composite dropped 11.61 points, or 0.38%, to 3,035.47.
Technology shares helped cap losses, with Apple hitting a new high of $644 per share to briefly top a $600 billion market capitalisation.
The S&P is up nearly 10% so far this year but fell 2.6% in the past four sessions as investors questioned the economy's strength and the US Federal Reserve's resolve to continue flooding the market with easy cash.
Some analysts view the pullback as a buying opportunity, while others see it as the start of a long-awaited correction.
"We've been hanging around the lows... established after Friday; the market seems to be accepting these levels and that sets up the opportunity for another sharp move higher," said Tom Alexander, head of Alexander Trading in Savannah, Georgia.
"However, if we take the lows out this could be the beginning of something bigger to the downside," he said.
Many analysts are focusing on the S&P's 50-day moving average as the support level that will make or break the current uptrend.
Friday's soft US payrolls report added to recent losses in the US stock market sparked by last week's minutes from the Fed's March policy meeting that were interpreted as showing the central bank as less than keen to launch more stimulus.
The S&P on Tuesday hit a low near 1,375, testing support at its 50-day moving average, now near 1,372.5. Monday's decline was the biggest in more than a month on the S&P, but trading volumes were the second-lowest so far this year.
Supervalu Inc shares jumped 7% to $5.69 after the third-largest US supermarket operator reported better-than-expected earnings and issued a full-year profit forecast above Wall Street's view.
Best Buy shares hit their lowest since December 2008 and were at their session low after Chief Executive Brian Dunn resigned after 28 years with the world's largest consumer electronics retail chain. Shares last traded down 2.3% at $22.11.
Dow component Alcoa Inc, a bellwether for the industrial sector, unofficially kick-starts the quarterly earnings season after the closing bell.