Elsewhere in the commodities markets, energy and industrial metals prices slumped, while gold prices edged higher.

Wheat prices have climbed roughly 70 percent since May on an explosive combination of strong worldwide demand and shrinking supply. Foreign buyers have been undeterred so far by the sharp run-up in prices, as countries -- worried by this year's paltry harvests in major producing regions -- try to lock in supplies of wheat.

The market has been watching the wheat crop in the Southern Hemisphere. Dryness continues to plague Australia's crop and has hurt expectations for yields in that country. Wheat supplies worldwide have dwindled rapidly this year after crops in the U.S., Europe and elsewhere were damaged by poor weather.

December wheat jumped 22.5 cents to $8.66 a bushel on the Chicago Board of Trade. The price of wheat has climbed about $3.40 since April 30.

"Clearly, wheat prices have reached a panic state," said Thomas R. Willis Jr., vice president and trader with Mesirow Financial in Chicago. "They are inflated. In two months I don't think we'll be at this level."

He noted, however, that index funds hold significant long positions in the wheat market, or bets that prices will rise, and those aren't likely to sell until the first week of November when the December futures contract is rolled over.

Corn prices slipped, meanwhile, while soybeans rose on the CBOT.

Outside the agriculture market, base metals prices fell Monday as inventories of aluminum, zinc and nickel swelled. Chinese demand for industrial metals has been a major driver of higher prices. But this year, Chinese smelters have upped their zinc output sharply and increased exports, putting pressure on prices. Zinc, which has slid 35 percent so far this year, fell 3.9 percent from Friday's close on the London Metal Exchange.

Copper prices sagged on the LME and on the New York Mercantile Exchange. December copper fell 1.8 cents to $3.2335 a pound at midday on the Nymex, as declines across the complex dragged prices lower.

The commodities markets in recent weeks have suffered the effects of uncertainty in the financial markets, credit tightness and worries about the pace of economic growth. JPMorgan analysts said in a note on Monday "credit market stress and a U.S. slowdown will not hit commodities equally. Base metals and energy should fare the worst, and precious metals the best."

The gold market attempted to extend its recent rally on Monday, after prices rose 4 percent over the past week. Gold broke through $700 last week as the U.S. dollar lost ground against other major currencies. With the dollar trading mixed on Monday, December gold rose 60 cents to $710.40 an ounce.

Analysts increasingly expect the Federal Reserve to lower the benchmark federal funds rate at its Sept. 18 meeting. Expectations for an interest rate cut have already undermined the dollar and bolstered gold, as investors have sought a haven from inflation.

Silver and platinum prices followed the broader industrial metals market lower.

Meanwhile, energy prices fell moderately on Monday, as the market priced in speculation that OPEC may go for a surprise increase in crude output when the group meets on Tuesday. The Organization for Petroleum Exporting Countries, which produces about 40 percent of the world's oil, had long been expected to hold production levels steady at the meeting.