U.S. soybeans fell slightly on Monday to consolidate after a six-day rally fueled by exports, as investors braced for a government crop report later in the day that could raise the official U.S. harvest forecast to a new record.
Corn eased as the cereal market also took a breather after a run of six rising sessions, while wheat edged down.
Driven by recent strong demand for U.S. exports, soybeans hit a two-week high last week, but the run-up to the U.S. Department of Agriculture's (USDA) monthly supply and demand report has turned attention back to the upcoming harvest, expected to be the biggest ever.
The most active soybean futures on the Chicago Board of Trade had fallen 0.6 percent to $9.74 a bushel by 1137 GMT.
"The market's ideas about supply...will be tested by tonight's (USDA) update, analysts are expecting a slight upward revision to U.S. yields," said Tobin Gorey, director of agricultural strategy at Commonwealth Bank of Australia.
The USDA is likely to raise its soybean yield forecast in its September supply and demand outlook due at 1600 GMT on Monday, according to a Reuters poll of analysts.
At the same time, analysts anticipate on average that the USDA will leave unchanged its forecast of 2016/17 U.S. soybean ending stocks, as recent export demand is seen trimming opening stocks going into the season and offsetting raised production.
The most active corn futures contract fell 0.4 percent to $3.39-3/4 a bushel. The contract had recovered from multi-year lows at the end of last month to reach a two-week high of $3.42 on Friday, a level it touched again earlier on Monday.
The USDA is expected to reduce its corn yield forecast. However, corn production and stocks would still be abundant, which combined with ample global wheat supplies have maintained a bearish price view among investors.
"Markets are still under pressure in cereals in a context of bumper supplies and a lack of enthusiasm from the buying side, despite historically low prices," consultancy Agritel said in a note.
The most active wheat futures contract fell 0.3 percent to $4.02-1/2 a bushel.
After big harvests in the United States and the Black Sea region, expectations are growing for a bumper wheat crop in Australia later this year.
The country could produce a near-record 28 million tonnes of wheat after favorable weather, a Reuters survey showed.
U.S. Commodity Futures Trading Commission data released after the close of trading on Friday showed large speculators expanded their net short bets in corn and wheat in the week to Sept. 6.
(Editing by Joseph Radford and Susan Thomas)