Wall Street made a brief incursion into positive territory early Thursday, but spent the rest of the day in the red as trepidation about weak data sent markets into a spin.
At the close, the Dow Jones Industrial Average was down 62 points with Hewlett-Packard, Bank of America, Intel and Caterpillar all taking a pummeling.
"The weakness comes ahead of a key nonfarm payrolls report tomorrow morning," said stock analysts at Briefing.com.
The Dow stood at 13,206.59 at the close.
As traders braced for the US unemployment report, released early Friday, the positive start to the day quickly became a memory.
It had started with news that fewer Americans claimed unemployment benefits than expected.
But weak data showing the all-important service sector of the US economy grew more slowly in April than March, instilled a little gloom that quickly spread to all sectors.
Economist expect Friday's jobs report to show the economy created a meager 162,000 jobs last month, while the unemployment rate was stuck at 8.2 percent.
The materials, energy and technology sectors were hardest hit.
Green Mountain Coffee Roasters shares lost nearly half of their value as the company trimmed its earnings outlook.
Weight Watchers shares lost over 19 percent of their value on poor earnings.
The S&P 500 fell 10.74 points (0.77 percent) to 1,391.57.
The Nasdaq was down slightly more, off 35.55 points (1.16 percent) to 3,024.30.
The bond market was slightly down. The 10-year Treasury yield rose by a fraction to 1.92 percent, while the 30-year was flat at 3.11 percent.
Bond prices go down as yields go up.