Crop prices fell. Prices for metals were mixed.
Crude oil for October delivery fell $1.01 to close at $109.52 a barrel in New York.
Oil had been rising over the past two weeks as tensions mounted over Syria and President Barack Obama pressed the case for a military strike in response to Syria's alleged use of chemical weapons on civilians.
On Monday there was reason to hope for a possible diplomatic solution when Syria's foreign minister welcomed a suggestion floated by U.S. Secretary of State John Kerry to move all the country's chemical weapons under international control.
In other energy trading, wholesale gasoline fell 5 cents to $2.80 per gallon, natural gas rose 8 cents to $3.61 per 1,000 cubic feet and heating oil retreated 5 cents to $3.12 per gallon.
Gold for December delivery edged up 20 cents to $1,386.70 an ounce. December silver fell 17.40 cents to $23.717.
December copper rose 16.5 cents to $3.2780 a pound.
October platinum fell $12.70 to $1,483 an ounce and December palladium fell $13.85 to $683 an ounce.
Wheat, soybeans and corn all fell.
December wheat fell 6.5 cents to $6.4125 a bushel. December corn fell 4.75 cents to $4.635 a bushel and November soybeans fell 11.25 cents to $13.565 a bushel.