CHICAGO: US corn futures fell for a second straight session on Tuesday and touched a three-week low after US Department of Agriculture data unexpectedly showed an improvement in US crop conditions.

Soyabean prices also eased, despite a decline in the USDA's weekly crop rating for the oilseed, as the weather outlook remained broadly favorable for US Midwest soya and corn crops after a recent dry spell.

Wheat was mixed on short-covering after prices touched multi-month lows late last week, although improving prospects for northern hemisphere harvests continued to hang over the market.

Chicago Board of Trade July corn futures fell 3-1/4 cents to $3.25 a bushel by 12:33 p.m. CDT (1733 GMT), after earlier dropping to its weakest since June 3. July soyabeans were down 1-3/4 cents at $8.74-1/2 a bushel and CBOT July wheat was up 1/2 cent at $4.85-1/2 a bushel.

Selling in corn and soyabeans was fueled by recent US crop-boosting rains and expectations that a high-pressure ridge forecast to bring crop-stressing heat next week could be short-lived.

"The weather forecast for the next couple of weeks looks fairly favorable," said Terry Reilly, senior commodities analyst with Futures International.

The USDA rated 72% of the US corn crop in good to excellent condition in its weekly crop progress report, up 1 percentage point from a week ago. Analysts polled by Reuters had expected a slight decline.

Soyabean traders were assessing developments in China after a recent flurry of soyabean purchases and news that some Chinese buyers are asking exporters to guarantee shipments are free of the novel coronavirus.

The soya market rebounded from early lows after White House trade adviser Peter Navarro walked back an earlier comment that the US-China trade pact was "over."