The Standard & Poor’s GSCI gauge of 24 raw materials fell 1.4 percent to settle at 635.82 at 4 p.m. in New York, paced by grains.
The UBS Bloomberg CMCI index of 26 prices declined 0.9 percent to 1,554.94.
Corn fell from a record after livestock producers hurt by higher feed costs urged the U.S. to suspend an alternative-fuel mandate that is driving grain demand from ethanol makers.
On the Chicago Board of Trade, corn futures for December delivery dropped 1.1 percent to $8.0525 a bushel, after touching an all-time high of $8.205.
Wheat futures for September delivery fell 2.9 percent to $8.8825 a bushel. The grain, which competes with corn in livestock feed, surged 17 percent this month.
Soybean futures for November delivery declined 0.2 percent to $16.41 a bushel.
Sugar dropped for the first time in three sessions as dry weather allowed the harvest to quicken in Brazil, the world’s top producer.
On ICE Futures U.S. in New York, raw sugar for October delivery declined 0.7 percent to 22.64 cents a pound. The sweetener jumped 7.8 percent in July, the second straight advance, after heavy rains in June delayed harvesting and exports from Brazil.
Cocoa futures for September delivery climbed 1.5 percent to $2,376 a metric ton.
Cotton futures for December delivery rose 0.3 percent to 71.34 cents a pound.
Arabica-coffee futures for September delivery fell 2.2 percent to $1.744 a pound.
Orange-juice futures for September delivery declined 2.1 percent to $1.099 a pound.
Gold declined, ending a four-session rally, as consumer confidence rose for the first time in five months, easing pressure on the Federal Reserve to announce measures to boost growth.
On the Comex in New York, gold futures for December delivery fell 0.6 percent to $1,614.60 an ounce, the first drop since July 24.
Silver futures for September delivery slipped 0.4 percent to $27.914 an ounce.
On the New York Mercantile Exchange, platinum futures for October delivery climbed 0.4 percent to $1,416.90 an ounce. Palladium futures for September delivery increased 0.4 percent to $590.55 an ounce.
Copper rose to the highest in more than a week as plans in China to increase spending on railroads and other projects boosted the outlook for demand in the world’s largest consumer of the metal.
On the Comex, copper futures for September delivery climbed less than 0.1 percent to $3.4175 a pound, after rising to $3.457, the highest for a most-active contract since July 20. 2012.
On the London Metal Exchange, copper for delivery in three months advanced 0.2 percent to $7,560 a metric ton ($3.43 a pound). Nickel, aluminum, lead, zinc and tin fell in London.
Crude oil fell for a second day on speculation that the Federal Reserve will be less likely to announce additional measures to stimulate the economy after U.S. consumer confidence and business activity unexpectedly grew.
On the New York Mercantile Exchange, oil futures for September delivery dropped 1.9 percent $88.06 a barrel.
Brent crude for September settlement decreased 1.2 percent to $104.92 a barrel on the London-based ICE Futures Europe exchange.
BP Plc, Trafigura Beheer BV and Royal Dutch Shell Plc sold cargoes of North Sea Forties crude. OAO Rosneft failed to buy Russian Urals in northwest Europe at a higher price.
Rosneft sold four cargoes of 100,000 metric tons each of Primorsk Urals crude to Shell and Vitol Group via a tender, according to three traders who declined to be identified because the information is confidential.
Gasoline declined as Sunoco Inc. may start a fluid catalytic cracker at the largest East Coast refinery and as Enbridge Inc. may reopen an oil pipeline tomorrow that serves the Chicago area.
On the Nymex, gasoline futures for September delivery fell 1.6 percent to $2.7743 a gallon.
Heating-oil futures for September delivery dropped 1.2 percent to $2.848 a gallon.
Natural gas declined in New York as revised weather forecasts showed cooler mid-August weather in the Northeast that may reduce the demand from electricity generators.
On the Nymex, gas futures for September delivery dropped 0.2 percent to $3.209 per million British thermal units.
U.K. natural gas for today declined as flows to St. Fergus in Scotland increased following an earlier disruption.
Within-day gas fell as much as 0.9 percent and traded down 0.4 percent at 53.7 pence a therm at 4:30 p.m. London time, according to broker data compiled by Bloomberg. Gas for this winter was little changed, heading for a fourth consecutive monthly decline. It traded at 63.05 pence a therm after reaching a 17-month low of 61.85 pence on July 23. A therm is 100,000 Btu.
Cattle fell, marking the biggest drop in almost seven weeks, on signs of increasing U.S. beef supplies as worsening crop conditions spurred ranchers to send more animals to slaughter.
On the Chicago Mercantile Exchange, cattle futures for October delivery slumped 1.1 percent to $1.244 a pound, the biggest loss for a most-active contract since June 13.
Hog futures for October settlement fell 2 percent to 80.3 cents a pound.
Feeder-cattle futures for August settlement gained 0.3 percent to $1.38625 a pound.
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