The most-active corn futures on the Chicago Board of Trade were up 0.1 percent at $3.68 a bushel at 0956 GMT after rising to a peak of $3.69-1/2 - the highest since Sept. 5.

"US weather is likely to interrupt harvesting in some corn regions," said Tobin Gorey, director of agricultural strategy, Commonwealth Bank of Australia.

Weather forecasters expect heavy rain across much of the western and central Midwest over the next week, likely soaking mature corn and soybeans in major producing states including Iowa, Illinois and Minnesota.

The most-active CBOT soybean futures rose 0.1 percent at $8.60 a bushel.

The US Department of Agriculture said exporters sold a net 1.43 million tonnes of corn last week and a net 1.52 million tonnes of soybeans, both near the high end of a range of trade estimates.,,

Wheat prices were higher, boosted by concerns about potential disruptions to shipments from Russia and drought in Australia.

The most-active CBOT wheat futures were up 0.7 percent at $5.21-1/2 a bushel.

"Despite denials from the authority in question, the market clearly still expects that wheat shipments from Russia may soon be restricted. What is more, crop estimates for Australia are being revised further downwards," Commerzbank said in a market note.

Wheat prices were boosted earlier this week by reports that Russian authorities may suspend operations in 30 grain loading points in two of the country's top exporting regions.

The country's safety watchdog subsequently said it had no immediate plans to do so.

The heaviest rain in years has fallen across parts of drought-parched inland Australia, bringing relief to struggling farmers but likely not enough water to break a dry spell that has crippled the country's most productive farmland.

December milling wheat on Paris-based Euronext was up 0.1 percent at 203 euros a tonne.