U.S. stocks headed for their lowest close in almost four weeks amid a rout in technology shares and as the selloff in commodities resumed on concern that slowing global growth will exacerbate supply gluts.

Tech companies, the market's best-performing sector over the past two months, bore the brunt of Wednesday's decline, which pushed the Standard & Poor's 500 Index toward its lowest level since Nov. 13. U.S. crude erased earlier gains, extending losses at a six-year low. The Bloomberg Dollar Spot Index sank and Treasuries fell ahead of next week's Federal Reserve meeting, while New Zealand's currency jumped after the central bank cut interest rates, but said it expects to achieve its inflation goal within current settings.

The selloff in commodities has clouded prospects for recoveries in the U.S. and Europe as capital spending from oil producers and miners wanes at the same time as China's economy shows few signs of firming. The raw materials slide has also kept inflation below central-bank targets one week before the Fed is expected to boost borrowing costs for the first time in a decade. This has exacerbated the divergence in monetary policy globally with officials from Europe to Japan still favoring stimulus measures.

The S&P 500 fell 0.7 percent as of 3:42 p.m. in New York, erasing an earlier advance of 0.8 percent. The gauge plunged through its average price for the past 50 days for the first time in two months, while a Goldman Sachs Group Inc. index of stocks with the highest short interest tumbled for a sixth day.

The technology-heavy Nasdaq 100 Index retreated 1.6 percent, as Apple Inc. slid 2.3 percent. Costco Wholesale Corp. sank 5.2 percent, the most in three years, after the largest warehouse-club chain in the U.S. reported below-estimate earnings.

DuPont Co. jumped 11 percent and Dow Chemical Co. rallied 12 percent as people familiar with the matter said a deal could be announced as soon as this week. Raw-materials producers, a group that includes the two chemical companies, rallied 3 percent for the best performance in the S&P 500.

West Texas Intermediate crude fell another 0.9 percent to $37.16 a barrel in New York as investors discounted a decline in U.S. oil inventories. Supplies fell by 3.57 million barrels last week, the U.S. Energy Information Administration reported Wednesday. Stockpiles along the Gulf Coast tumbled 7.3 million barrels, the biggest drop since December 2012.

Oil is still trading near levels last seen during the global financial crisis as Saudi Arabia leads the Organization of Petroleum Exporting Countries in maintaining output and defending market share against higher-cost producers, fueling a record supply glut.

Gold futures fluctuated near $1,076.50 an ounce, while contracts on copper advanced 0.7 percent.