Chicago soybeans and corn futures edged down on Friday to stay on course for a weekly loss as the start of the autumn harvest season kept attention on the prospect for bumper crops.
Wheat also ticked lower to head for a weekly drop as abundant global supplies pressure a market that is also facing uncertainty over demand from top importer Egypt, whose strict terms relating to a grain fungus have put off traders.
Chicago Board of Trade most-active soybeans inched down 0.1 percent to $9.49-1/4 a bushel by 1107 GMT, while corn lost 0.5 percent to $3.28-1/2 a bushel.
Wheat edged 0.2 percent lower to $3.98-3/4 a bushel.
For the week, soybeans and corn have each lost more than 3 percent and wheat over 1 percent.
"People in the soybean market appear to be focused on the size of the U.S. harvest. But it could be a matter of timing and if export demand remains strong going forward then prices could find support," Alexandre Boy of consultancy Agritel said.
"The U.S. corn harvest is coming, and going to weigh on the wheat market too."
A higher than expected estimate of the soybean harvest by the U.S. Department of Agriculture in a monthly report on Monday sapped the oilseed market and countered support from a run of export sales to China.
However, the USDA announced on Thursday that private exporters sold 110,000 tonnes of U.S. soybeans to unknown destinations, a first such daily soybean sales announcement in a week.
The USDA reported separately on Thursday weekly export sales of U.S. soybeans at more than 1 million tonnes, in line with trade expectations. U.S. soy processors, meanwhile, crushed 2.6 percent fewer beans in August than a year ago and the pace fell below market expectations due to declines at plants in the Southwest, the National Oilseed Processors Association (NOPA) said.
In corn, weekly exports sales of 703,500 tonnes for 2016/17 fell below the range of trade expectations.
In wheat, Egypt's import policy continue to put a question market over international demand at a time of large supplies.
Egypt's state grain buyer GASC is holding a tender on Friday, after canceling a previous one in which it received just one offer.
Egypt's adoption of a zero-tolerance policy on ergot, a grain fungus, in imported wheat has discouraged suppliers who say zero content is virtually impossible to guarantee and who support a switch back to an internationally recognized standard allowing for traces of ergot.