SINGAPORE - Chicago wheat slid nearly 1% for the first time in three sessions on Tuesday, with ample supply from the Black Region and expectations of an above-average crop in Australia weighing on the market.

Corn eased as record harvest in the United States is set to enter the world market while soybeans fell for a second session amid a lack of Chinese demand.

"We have seen strong harvests in several exporting countries and the outlook for Australian crop is also promising," said one grains trader in Singapore. "Prices in exporting countries are coming under pressure as there are no supply-side issues as of now."

The most-active wheat contract on the Chicago Board of Trade (CBOT) slid 1% to $5.29 a bushel, as of 0246 GMT. Corn lost 0.6% to $4.17-3/4 a bushel and soybeans fell 0.8% to $10.46-1/4 a bushel.

Abundant production from Northern Hemisphere harvests and an improving outlook for crops in Southern Hemisphere exporters Argentina and Australia weighed on wheat prices.

Australia's wheat output is poised to be 22% above the 10-year average at 33.8 million metric tons on the back of largely crop-friendly growing conditions, the agriculture ministry said.

Russian export prices continued to decline last week amid more active arrivals of the new crop, while analysts again revised up estimates of August shipments.

For corn and soybeans, favourable prospects for U.S. harvest kept a lid on prices.

Soybean prices have risen in recent weeks, buoyed by hopes that China would revert to buying U.S. crops after months of shunning the origin in a wider trade war with Washington. But no such purchases have been confirmed.

Traders will be monitoring U.S.-Chinese talks in the coming days, with senior Chinese trade negotiator Li Chenggang expected in Washington.

Large speculators trimmed their net short position in CBOT corn futures in the week ended August 26, regulatory data released on Friday showed.

The Commodity Futures Trading Commission's weekly commitments of traders report also showed that non-commercial traders, a category that includes hedge funds, trimmed their net short position in CBOT wheat and trimmed their net short position in soybeans.