U.S. stocks fell on Wednesday on lingering concerns over an economic recovery and anxiety about the health of corporate profits ahead of the second-quarter earnings season.

Alcoa Inc , the first Dow component to report, is expected to post its third consecutive quarterly loss after markets close on falling demand for aluminum.

After a rally took the S&P 500 index up 40 percent from 12-year lows in early March, traders have been disappointed that recent economic data, especially the weaker-than-expected June payroll report, has not pointed to an economic rebound.

Stocks initially opened higher but the gains didn't last as investors remained cautious.

Craig Phares, managing director of equity division at Nomura Securities International in New York, said unemployment and a lack of consumer spending could hurt corporate profits.

We saw some pretty heinous jobless numbers last week. With employment figures continuing to be bad, you have to think there's very little case to be made for positive consumption, said Phares.

The Dow Jones industrial average <.DJI> slipped 22.22 points, or 0.27 percent, to 8,141.38. The Standard & Poor's 500 Index <.SPX> was off 5 points, or 0.57 percent, to 876.03. The Nasdaq Composite Index <.IXIC> gave up 9.62 points, or 0.55 percent, at 1,736.55.

Energy shares declined as crude oil futures fell 3.5 percent to a more than six-week low. Refined product inventories rose sharply last week, according to new data, suggesting that demand is faltering.

Chevron Corp shares fell nearly 1 percent to $62.19 and were among the biggest drags on the Dow industrials.

Microsoft Corp fell after Google Inc said it will launch a new operating system in the second half of 2010, taking on Microsoft's core business.

Microsoft stock declined 2 percent to $22.09.

Leaders of the Group of Eight richest nations and the major developing powers gathered for a three-day summit in Italy. They are expected to agree the world's economy is still too weak to remove stimulus measures. [ID:nL8395794]

(Reporting by Rodrigo Campos; additional reporting by Caroline Valetkevitch; editing by Jeffrey Benkoe)