* Soybeans drop more than 1%

* Forecast of rains in Brazil ease dryness concerns

* Grain markets await Argentina policy

(New throughout, updates prices, market activity, adds US trading comments; changes dateline, previous PARIS/SINGAPORE)

CHICAGO, Dec 13 (Reuters) - Chicago soybean futures sank for a second session on Wednesday as the prospect of rain in Brazil eased worries about drought damaging harvest prospects in the world's top soybean exporter.

Corn and wheat futures also traded lower.

The most active soybean contract on the Chicago Board of Trade (CBOT) was down 1.2% at $13.08 a bushel at 1700 GMT.

The market toppled under pressure from forecasts in central and northern Brazil that show some much-needed rain is likely on its way in the week ahead, in the region where hot, dry conditions have been a cause of concern.

"Well welcome to the wonderful world of weather," said Tom Fritz, a partner with brokerage EFG Group in Chicago. "We're trading the forecast for next week, which has temperatures moderating and bringing back some normal moisture."

The selloff came despite the U.S. Department of Agriculture confirming sales of 125,000 metric tons of U.S. new-crop soybeans to unknown destinations, given that delivery for the crop is far off in the 2024/25 marketing year that begins Sept. 1, 2024.

Traders were also monitoring headlines from Argentina, where the peso dropped more than 50% as markets watched the first details of new President Javier Milei's plans to steer the beleaguered economy back on track. Argentina is one of the world's top exporters of processed soy oil and meal, the No. 3 for corn and important producer of wheat.

CBOT corn lost 0.8% to $4.81-1/2 a bushel, and wheat slid 2.5% to $6.10 a bushel after rallying to a four-month high last week on the back of U.S. wheat sales to China.

Global demand from places like

Algeria

and

Tunisia

helped push futures higher on Tuesday. But without much demand in the news on Wednesday, wheat lost those gains from a day earlier.

"The bull market needs to be fed every day," Fritz said. (Additional reporting by Gus Trompiz in Paris and Naveen Thukral in Singapore; Editing by David Gregorio)