CANBERRA - Chicago wheat futures fell for a fourth consecutive session on Tuesday as ​rainfall eased drought conditions ⁠in U.S. cropping zones and traders positioned for fresh supplies from ‌Northern Hemisphere harvests. Corn and soybean futures also slipped, as expectations of a U.S.-Iran peace deal ​raised the prospect that fuel and fertiliser could flow more freely from the Gulf, easing ​supply shortages.

The most-traded ​wheat contract on the Chicago Board of Trade (CBOT) was down 1.2% at $6.38-1/2 a bushel at 0338 GMT, with CBOT corn falling 1.1% to $4.58-1/4 ⁠a bushel and soybeans trading 0.7% lower at $11.88-1/2. Wheat has slipped around 7% from a two-year high of $6.88-1/4 on May 14, but remains roughly 25% above its level at the start of the year, largely due to drought damage to ​U.S. crops.

Rain ‌has fallen or ⁠is forecast in ⁠the coming days across much of the U.S. wheat belt. "That rain presents a chance ​to halt the decline in crop yields," said Tobin ‌Gorey, founder of agricultural consultants Cornucopia.

"Warm temperatures, though, might ⁠work against such a halt," he added. Also keeping prices in check is the prospect of new grain hitting the market in the coming months from Northern Hemisphere nations that grow the bulk of the world's wheat, many of which expect good harvests. Argentina's government, meanwhile,said it would reduce export taxes, which could support production and shipments, and the European Union saidit would temporarily lift customs duties on key nitrogen-based fertilizers to help farmers cope with price rises. Large ‌speculators remain net short CBOT wheat and net long ⁠corn and soybeans, though they cut the size of ​their positions in the week to May 19, regulatory data showed.

On the demand side, Brazil's energy policy council, CNPE, is expected to approve raising the mandatory ethanol ​blend in gasoline to ‌32% from 30%. Strong biofuel demand has supported crop ⁠prices in recent months.