Stocks fell on Wednesday as investors worried about the outlook for profits after Alcoa Inc's earnings missed estimates and Chevron Corp joined companies issuing profit warnings.

Investors had hoped Alcoa would deliver a strong start to the third-quarter earnings season on Tuesday, but disappointing earnings and lowered outlooks from companies ranging from paper products to pet supplies signaled a slowing economy was taking its toll on earnings.

Chevron shares dropped nearly 2 percent and were among shares leading the S&P 500 lower, along with rival Exxon Mobil Corp., which also dragged on the Dow..

The market is very uncertain, said Joseph Battipaglia, market strategist at Stifel Nicolaus in Philadelphia.

The market does not have the necessary propellent to move to higher levels because you don't have a re-acceleration in the growth rate, you have a deceleration in the economy. The earnings are going down in terms of growth.

The Dow Jones industrial average was down 47.72 points, or 0.34 percent, at 14,116.81. The Standard & Poor's 500 Index was down 5.48 points, or 0.35 percent, at 1,559.67. The Nasdaq Composite Index was down 1.09 points, or 0.04 percent, at 2,802.82.

Shares of Alcoa slid more than 3 percent to $38.22 on the New York Stock Exchange. It was the biggest drag on the Dow.

Shares of Chevron dropped 1.9 percent to $90.94, while shares of rival Exxon Mobil fell 0.9 percent to $91.75.

Petsmart Inc, the biggest U.S. pet supplies retailer, cut its outlook, sending shares 5 percent lower to

$30.52.

International Paper, which also warned about its profit outlook, fell 2.4 percent to $36.17. It blamed weak land sales while Chevron blamed weak refining margins.

Costco Wholesale Corp was among the market's bright spots after the No. 1 U.S. warehouse club operator posted a higher quarter profit. Its stock was up 7 percent at $67.77 on the Nasdaq.

U.S.