* The USDA delayed the release of its weekly US Crop Progress report until Tuesday at 11 a.m. CDT (1600 GMT) due to technical difficulties.
* The US Department of Agriculture is scheduled to update its monthly supply and demand projections on Wednesday.
* CBOT September futures contracts will expire on Friday.
WHEAT - Down 5 to 7 cents per bushel
* Wheat futures retreat after prior-session rally as traders square positions ahead of Wednesday's USDA report. Sluggish US export demand weighing on prices despite shrinking global crops.
* Australia's ABARES reduced its wheat forecast by nearly 13 percent.
* Bulgaria harvested 6.3 percent less wheat this year than a year ago due to adverse weather, the agriculture ministry said.
* Iraq will cut the irrigated area it plants with wheat by half in the 2018-2019 growing season due to water shortages, officials told Reuters.
* The CBOT reported 3 deliveries against the CBOT September soft red winter wheat contract and no K.C. September hard red winter wheat deliveries. There were also no MGEX September spring wheat deliveries.
* CBOT December wheat last traded down 7 cents at $5.21-1/4 per bushel. K.C. December hard red winter wheat was last down 6 cents at $5.24-3/4 and MGEX December spring wheat was down 5-1/2 cents at $5.74-1/2 per bushel.
CORN - Steady to down 2 cents per bushel
* Weak cash market and forecasts for a bumper US harvest weigh on futures as traders square positions ahead of Wednesday's USDA report.
* Brazil's Conab trimmed its corn crop forecast on Tuesday.
* The USDA on Tuesday confirmed private sales of 138,000 tonnes of US corn to South Korea.
* There were 220 CBOT September corn deliveries reported.
* CBOT December corn last traded unchanged at $3.67-1/4 per bushel.
SOYBEANS - Steady to down 2 cents per bushel
* Futures ease ahead of Wednesday's USDA report, when the agency is expected to increase its US soy crop forecast and raise its stocks estimate.
* Brazil's Conab raised its soy crop forecast to the second highest on record.
* The USDA on Tuesday confirmed cancellations of 192,000 tonnes in US soybean export sales to unknown destinations.
* CBOT September soybean deliveries totaled 139 contracts. CBOT September soyoil deliveries totaled 357 contracts and September soymeal deliveries totaled 20 contracts.
* CBOT new-crop November soybeans last traded 2-3/4 cents lower at $8.42-1/2 a bushel.