Wheat edged higher for a second day, supported by risks to US spring planting from snow storms and improving export prospects, though the cereal was another commodity set for a weekly loss.
The most-active corn contract on the Chicago Board of Trade was up 0.2 percent at $3.60-3/4 a bushel by 1107 GMT but down 0.5 percent this week.
The corn market has found some support from potential disruption to planting from extreme weather in the US Midwest in the past month. But delays to field work have been set against massive US stockpiles, the prospect of a bumper South American harvest and this week's US export data.
"The corn market is heavy and there could be a record South American harvest if you combine the Brazil and Argentina crops," said Nathan Cordier at consultancy Agritel.
"The US is struggling with exports and the lag in corn export sales is continuing."
The US Department of Agriculture (USDA) on Thursday reported corn export sales in the week to April 4 at 548,000 tonnes, below trade expectations.
Soybean export sales at 280,400 tonnes were well below a range of trade estimates.
CBOT soybeans were up 0.2 percent at $8.96-3/4 a bushel and, like corn, showed a slight decline for the week.
The Buenos Aires Grains Exchange on Thursday raised it forecast for Argentina's soybean harvest to 55 million tonnes, a day after the Rosario exchange increased its estimate for the crop.
Brazilian agricultural statistics agency Conab, meanwhile, raised its estimates for the country's soy and corn harvests.
CBOT wheat was up 0.6 percent at $4.63-1/4 percent but was down 1 percent over the week.
A second "bomb cyclone" blizzard was limiting movement of crops in the US Midwest and Plains on Thursday. There was some concern that spring wheat planting in northerly regions could be delayed, though analysts said snowfall could offer beneficial moisture for winter wheat.
The wheat market was awaiting the outcome of an Egyptian tender to see if US wheat would repeat its success in the North African country's previous tender.
A purchase of 540,000 tonnes of optional-origin wheat by Algeria on Thursday could be sourced partly in the United States because of competitive US prices that were challenging French wheat, traders said.