GRAINS-Corn eases from six-week high, soy and wheat stay weak

By Gus Trompiz and Naveen Thukral

PARIS/SINGAPORE, Sept 3 (Reuters) - Chicago corn edged lower on Wednesday, pausing after a six-week high as traders set brisk export demand and a decline in crop ratings against the prospect of a bumper U.S. harvest.

Soybeans eased, with a lack of Chinese buying keeping a lid on the market, while wheat extended a day-earlier fall linked to ample global supplies.

The most-active corn contract on the Chicago Board of Trade (CBOT) Cv1 was 0.7% lower at $4.20 a bushel at 1203 GMT, after climbing to its highest since July 22 at $4.24-1/4 a bushel.

In a weekly report on Tuesday, the U.S. Department of Agriculture lowered its condition rating for corn crops, though the score remained the highest for the time of year since 2016.

The USDA reduced more sharply its rating for soybean crops, which traders have seen as more exposed to late-summer dryness in parts of the U.S. Midwest.

"Corn and soybean crop ratings have slipped slightly but we are still looking at very large U.S. crops," said one grains trader in Singapore. "It is hard for the market to sustain gains with such large supplies entering the market."

Corn had rallied on a run of strong U.S. exports and doubts over whether the harvest will be as big a record as projected by the USDA in mid-August.

"U.S. export flows ... will be critical to maintaining price support in the months ahead absent a material ... deterioration in harvest prospects," Rabobank analysts said in a note.

CBOT soybeans Sv1 ticked down 0.4% to $10.37-1/4 a bushel, holding near a one-week low struck on Tuesday.

A lack of new-crop U.S. soybean purchases by China, amid a wider trade battle between Beijing and Washington, is clouding the demand outlook for the oilseed market.

Beijing's hosting this week of non-Western leaders, including Russian President Vladimir Putin and Indian Prime Minister Narendra Modi, has underscored its rivalry with the United States.

CBOT wheat Wv1 was down 0.4% at $5.26-1/4 a bushel.

Falling prices in Russia, amid improving harvest prospects in the world's biggest wheat-exporting country, and expectations of an above-average crop in Australia have weighed on wheat markets this week.

Traders were nonetheless monitoring reports of excess rain in Argentina that could spoil what had been favourable field conditions for the upcoming wheat harvest there.