GRAINS-Soy at 2-week low on U.S. harvest, adjustments ahead of USDA

* Soyoil futures fall on biodiesel uncertainty

* Wheat retreats a day after recording one-month high

* Corn follows weak trend

* USDA's small grains, quarterly stocks reports awaited

(New throughout; updates prices, adds quotes, changes byline, dateline, previous PARIS/SINGAPORE) CHICAGO, Sept 28 (Reuters) - U.S. soybean futures fell to a two-week low on Thursday on pressure from the expanding U.S. harvest and technical selling a day ahead of key U.S. government crop reports, analysts said. Wheat and corn followed the lower trend as traders adjusted positions ahead of the U.S. Department of Agriculture's small grains and quarterly stocks reports, both due on Friday. Chicago Board of Trade November soybeans settled down 6 cents at $9.59-1/2 per bushel. CBOT December wheat ended down 6-1/2 cents at $4.55 a bushel and December corn fell 1-1/2 cents at $3.52-1/2 a bushel. Soybeans sagged on seasonal pressure as combines rolled in much of the Midwest crop belt amid favorably dry conditions for harvest. "Good U.S. weather has taken a toll on corn and bean prices," said Terry Reilly, senior commodity analyst with Futures International. Adding to the weak tone in soybeans was a slide in CBOT soyoil futures tied to uncertainty about demand for U.S. biodiesel fuel, which is made from soyoil. Soyoil has been under pressure since the U.S. Environmental Protection Agency on Tuesday said it was seeking comment on a proposal to reduce 2018 biodiesel blending requirements under the U.S. renewable fuel standard (RFS). "It's positioning ahead of the (USDA) report, plus the worries about the RFS," Reilly said of the declines in grains in soy. Meanwhile, Argentina's government is negotiating a minimum price for its biodiesel exports to the United States that it hopes could replace punitive tariffs implemented last month, a foreign ministry official told Reuters. CBOT soybeans fell despite the USDA reporting the third-largest weekly soybean export sales total on record, at just over 3.1 million tonnes for old- and new-crop marketing years combined. Of the total, 1.4 million tonnes of soybeans were earmarked for China, the world's top buyer. Chinese importers have been taking advantage of a harvest-time slide in U.S. soybean prices to ramp up buying at a time when supplies from rival exporter Brazil have thinned. CBOT wheat fell in a profit-taking setback a day after the December contract recorded a one-month high on technical buying and short-covering. Ahead of the USDA's small grains report, analysts surveyed estimate of U.S. 2017 wheat production. For corn, analysts expect the USDA to report U.S. Sept. 1 corn stocks at 2.353 billion bushels, which would be the largest since 1988.

CBOT settlement prices:

Net Pct Volume

Last change change

CBOT wheat WZ7 455.00 -6.50 -1.4 55519 CBOT corn CZ7 352.50 -1.50 -0.4 118768 CBOT soybeans SX7 959.50 -6.00 -0.6 97012 CBOT soymeal SMZ7 311.50 -1.80 -0.6 58654 CBOT soyoil BOZ7 32.82 -0.40 -1.2 100900

NOTE: CBOT December wheat, December corn and November soybeans shown in cents per bushel, December soymeal in dollars per short ton and December soyoil in cents per lb.

(Additional reporting by Naveen Thukral in Singapore and Gus Trompiz in Paris; Editing by David Clarke and Marguerita Choy)