U.S. stocks fell as oil prices reached a new high, spurring concern that rising energy costs will hamper earnings growth. The Dow Jones industrial average closed below 10,000 for the first time in six weeks.

Oil "is a source of worry when it's $50 a barrel and there's a risk of its moving higher," said Chris Trompeter, who helps manage $325 million at Tradition Capital Management in Summit, N.J. "That's clearly weighing on investors' minds because of the impact on consumer spending and the impact on business costs."

Carriers such as Delta Air Lines dropped on concern higher jet-fuel prices will add to the industry's losses.

The Dow average fell 58.70, or 0.6 percent, to 9988.54, its lowest level since Aug. 17. The Standard & Poor's 500-stock index dropped 6.59, or 0.6 percent, to 1103.52. The Nasdaq composite index declined 19.60, or 1 percent, to 1859.88.

Oil prices rose on concern that rebel attacks in Nigeria will reduce production and U.S. refiners will struggle to replenish supplies disrupted by Hurricane Ivan. Crude for November delivery gained 76 cents, or 1.6 percent, to $49.64 a barrel, in New York Mercantile Exchange floor trading. The price touched $50 in electronic trading after the floor closed.

Delta, the third-largest U.S. carrier, fell 32 cents, to $2.94. Its 9.8 percent drop was the biggest in the S&P 500. Continental Airlines, the No. 5 U.S. airline, slid 47 cents, to $8.30. JetBlue Airways declined $1.31 to, $20.56; AirTran Holdings dropped 55 cents, to $9.73; and Frontier Airlines Inc. slipped 22 cents, to $7.35.

United Technologies, which makes Pratt & Whitney jet engines, and 3M, the maker of Scotch tape, contributed the most to the decline in the Dow average. United Technologies slipped 87 cents, to $91.27, while 3M fell 99 cents, to $77.69.

Semiconductor shares declined after Morgan Stanley cut its rating on the industry, citing a "sharp" deceleration in revenue growth and weaker-than-expected third-quarter earnings forecasts.

Texas Instruments slipped 55 cents, to $21.14. Broadcom shed 75 cents, to $27.03.

Other Indicators

* The New York Stock Exchange composite index fell 35.00, to 6496.37; the American Stock Exchange index fell 1.83, to 1263.14; and the Russell 2000 index of smaller-company stocks fell 7.61, to 558.36.

* Declining issues outnumbered advancing ones by 9 to 5 on the NYSE, where trading volume rose to 1.26 billion shares, from 1.25 billion on Friday. On the Nasdaq Stock Market, decliners outnumbered advancers by 5 to 2 and volume totaled 1.3 billion, down from 1.35 billion.

* The price of the Treasury's 10-year note rose $3.13 per $1,000 invested, and its yield fell to 3.99 percent, from 4.03 percent on Friday.

* The dollar rose against the Japanese yen and fell against the euro. In late New York trading, a dollar bought 111.26 yen, up from 110.68 late Friday, and a euro bought $1.2300, up from $1.2268.

* Gold for current delivery rose to $409.10 a troy ounce, from $408.10 on Friday, on the New York Mercantile Exchange's Commodity Exchange.