Wheat also eased after multi-month highs that were supported by rising global prices and improved export sentiment. Corn edged higher.
The most-active soybean contract on the Chicago Board Of Trade was down 0.2 percent at $9.05 a bushel by 1314 GMT. The contract hit its highest since mid-June on Wednesday at $9.28.
The most active contract struck a near six-month high on Wednesday, while spot January futures reached a 4-1/2 month top, as traders reported China had booked its the first sizeable purchases of US soybeans in more than six months after a US-China truce in a tit-for-tat tariff war.
But confirmation on Thursday by the US Department of Agriculture (USDA) that private exporters sold 1.13 million tonnes of US soybeans to China left the market underwhelmed.
"Despite an announcement of a sale of 1.13 million tonnes, (export) sales are well below previous years' level," consultancy Agritel said.
"This could increase in dramatic proportions the ending stocks in the US just before the arrival of the Brazilian harvest."
The USDA on Tuesday left unchanged its forecast for US soybean stocks at the end of the 2018/19 marketing year at a record-high 955 million bushels, doubling from a year earlier.
The soybean market has been awash with rumours that China will purchase several million tonnes of the oilseed, as part of the detente phase in its trade battle with Washington, but there were no clear signs about further purchases.
Investors have also been weighing short-term gains from the truce against concerns of a broader negative effects on global growth from the unresolved trade dispute.
On the corn market, which has also been awaiting indications of possible Chinese buying of U.S cargoes, the most active CBOT contract was up 0.4 at $3.85-3/4 a bushel.
CBOT wheat was down 0.5 percent at $5.33-1/4 a bushel, consolidating after Thursday's three-month peak of $5.38-1/2.
In Paris, Euronext March wheat was flat at 207.50 euros a tonne, holding close to Thursday's two-month top of 208.00 euros.
Chicago and Paris futures have been buoyed by some improved export figures and signs that Russian wheat is becoming less competitive.
The USDA on Thursday reported weekly export sales of US wheat at 754,000 tonnes, the biggest tally since August.
Russia's agriculture ministry will hold a meeting with grain exporters on Dec. 21, Interfax news agency reported, feeding speculation that the world's biggest supplier might move to curb exports.