Soybeans set for first weekly loss in 6 as LatAm rains ease supply woes

* Soybeans, corn drop over 1% on Friday on improved weather

* Wheat down, although decline limited by Russian export duty

SINGAPORE, Jan 22 (Reuters) - Chicago soybean futures dropped almost 2% on Friday, with the market poised for its first weekly decline in more than a month, as rains in South American key growing areas improved crop yield prospects and assuaged worries about global supply.

Corn and wheat prices dropped more than 1%, with both markets also set for weekly loss.

"Grain and soybean markets are reversing some of the bullish trend seen in recent weeks," said one Singapore-based trader at an international trading company.

The Chicago Board of Trade (CBOT) most-active soybean contract nearly 5% this week, after closing firmer for the last five weeks. The market was down 1.8% at $13.46-1/4 a bushel, as of 0316 GMT.

Corn dropped 2.5% so far this week, its first decline in seven weeks, and wheat lost 3.4% this week after ending the previous week on a positive note.

Argentine soybean and corn planting sped forward over the last week, helped by rain that moistened fields parched by months of dry weather, the Buenos Aires Grains Exchange said on Thursday.

More moisture was needed over the short term to ensure good yields for the 2020/21 crop, the exchange said in a report.

Losses in soybean market were limited by private sales of 136,000 tonnes of U.S. cargoes to China and 163,290 tonnes to Mexico, both for shipment in the 2020/21 season, according to the U.S. Department of Agriculture.

Corn also benefited from export sales, as the USDA reported private sales of 336,500 tonnes of the U.S. corn to unknown destinations for shipment in the 2020/21 season.

Ukrainian milling wheat export prices exceeded $300 per tonne on Wednesday, supported by a sharp upward trend in Russia, analyst APK-Inform said on Thursday.

Russia said the country's wheat export prices rose sharply last week ahead of a new export tax imposed by one of the world's largest wheat exporters from mid-February.

Commodity funds were net buyers of CBOT corn, soyoil and soybean futures contracts on Thursday and net sellers of soymeal and wheat futures contracts, traders said. (Reporting by Naveen Thukral, Editing by Sherry Jacob-Phillips)