(Recasts, updates with U.S. trading, adds export sales data, changes byline/dateline; pvs LONDON)
CHICAGO, Dec 14 (Reuters) - U.S. soybean futures sagged to their lowest in more than four weeks on Thursday, weighed down by forecasts for much-needed rains in Argentina, traders said.
Wheat and corn futures were hovering near unchanged, steadying after short-covering bounces.
The most-active soybean contract on the Chicago Board of Trade was down 0.9 percent.
"Argentina's dry soybean crops remain an important prop for the market," Commonwealth Bank of Australia analyst Tobin Gorey said in a market update. "(But) weather forecasters are becoming less confident the hot and dry conditions will persist. Any suggestion of a rain event for the region might quickly undermine soybean prices."
Rains expected this weekend in Argentina's main soy and corn growing areas will provide some relief to drought-stricken parts of the country's central farm belt.
At 10:19 a.m. CST (1619 GMT), CBOT January soybean futures were down 8-3/4 cents at $9.70-1/2 a bushel. Prices bottomed out at $9.69-3/4 a bushel, their lowest since Nov. 15.
Soybean futures also hit technical resistance following Wednesday's rally, with the January contract failing to hold support above the 100-day moving average.
CBOT March soft red winter wheat futures were 1/2 cent higher at $4.17-1/4 a bushel.
Wheat futures were underpinned by bullish export data.
The U.S. Agriculture Department on Thursday morning said weekly export sales of wheat totalled 598,400 tonnes, topping market forecasts that ranged from 250,000 tonnes to 450,000 tonnes. A week ago, wheat export sales were 323,034 tonnes.
Dealers said, however, supplies remained abundant, keeping a lid on any potential gains in wheat futures.
Farm office FranceAgriMer cut its outlook for French 2017/18 soft wheat exports outside the European Union on Wednesday for the second month in a row to take account of intense competition on world markets.
CBOT March corn futures were unchanged at $3.49 a bushel. (Additional reporting by Naveen Thukral in Singapore and Nigel Hunt in London; Editing by Dale Hudson and Frances Kerry)