Chicago wheat futures extended losses on Friday, with the market set for a fourth weekly decline, pressured by ample Black Sea supplies that are giving stiff competition to US exporters.
Soybeans inched up after last session's deep losses, while corn fell.
The most-active wheat contract on the Chicago Board of Trade (CBOT) Wv1 slid 0.9% to $7.75-3/4 a bushel, as of 0152 GMT, soybeans Sv1 added 0.2% to $14.33-1/4 a bushel and corn Cv1 gave up 0.1% to $6.59-3/4 a bushel.
For the week, wheat is down almost 3%, corn has dropped nearly 2% and soybeans are little changed.
A record wheat production in Russia, the world's biggest exporter and ample supplies elsewhere from the Black Sea region are adding pressure on US futures.
The US Agriculture Department (USDA) said export sales of wheat totalled 162,500 tonnes in the week ended Nov. 24, well below the low end of analysts' forecasts that ranged from 300,000 to 725,000 tonnes.
The USDA reported weekly corn export sales of 632,700. The market had expected 475,000 to 1.1 million tonnes.
The soybean market dropped on Thursday after the US government proposed smaller-than-expected biofuels blending requirements.
The US Environmental Protection Agency proposed smaller increases than traders expected in the amount of ethanol and other biofuels that oil refiners must blend into their fuel over the next three years.
Production of renewable diesel, which can be made from soyoil, is growing, "but not at the unrealistic pace expected by fund managers," StoneX chief commodities economist Arlan Suderman said.
Soybeans and wider commodity markets had been underpinned in recent sessions by signs China was softening its tone on Covid-19 rules after rare public protests in the world's second-largest economy.
Argentina's wheat production outlook is likely to face more cuts due to lower-than-expected yields, the Buenos Aires grains exchange said on Thursday, as the harvest of the grains advances in the midst of a prolonged drought.
Commodity funds were net buyers of CBOT soymeal futures contracts on Thursday and net sellers of soybean, soyoil, corn and wheat futures, traders said.