SINGAPORE: Chicago soybean futures rose on Tuesday for a fourth consecutive session as a widely watched US report is expected to reduce forecast for world supplies amid adverse South American weather.

Wheat was little changed after Monday's fall on improved US weather, while corn slid after two straight sessions of gains.

"The USDA (US Department of Agriculture) report is likely to be bullish for soybeans," said one Singapore-based grains trader. "Harvest-time rains in Brazil have not only hit supplies but also the quality of beans."

The most-active soybean contract on the Chicago Board of Trade (CBOT) added 0.5% to $14.41-1/4 a bushel by 0320 GMT, having firmed 0.3% on Monday when prices hit a June 2014 high of $14.60 a bushel.

Corn futures lost 0.5% to $5.44-1/2 a bushel and wheat was unmoved at $6.46-1/2 a bushel.

Analysts expect the USDA will lower on Tuesday its estimates for 2020/21 ending stocks for soybeans and corn.

Brazilian farmers had harvested an estimated 35% of the planted soybean area through last Thursday, down from 49% a year earlier and the slowest pace in a decade, agribusiness consultancy AgRural said.

The quality of the crops is also being affected by damp conditions.

Wheat prices are under pressure on forecasts for showers in the southern Plains and Midwest.

The USDA rated 36% of the winter wheat in Kansas, the top US producer, in good to excellent condition, down from 37% a week earlier.

But ratings improved in Oklahoma, with 53% of the state's crop rated good to excellent, up from 46% the previous week.

Commodity funds were net buyers of CBOT soyoil, corn and soybean futures contracts on Monday and net sellers of wheat and soymeal futures, traders said.