GRAINS-U.S. soy, corn fall over 1 pct on big harvest forecasts

* Talk of hefty U.S. soy, corn yields as harvest expands

* Fresh export sales fail to lift bearish sentiment

* Trade looking ahead to USDA Oct. 12 supply, demand reports

* CBOT, MGEX wheat sag after USDA raises supply forecast

(Recasts throughout; updates prices, adds quotes; changes byline, dateline, previous LONDON) CHICAGO, Oct 2 (Reuters) - U.S. soybean and corn futures fell by over 1 percent on Monday on expectations of large harvests that should more than meet demand, adding to hefty inventories, traders said. Wheat futures also fell, with the spot Chicago Board of Trade contract nearing a two-week low, as traders continued to digest a larger-than-expected estimate of the U.S. 2017 spring wheat harvest. Chicago Board of Trade November soybeans settled down 11 cents at $9.57-1/4 per bushel and December corn finished down 3-3/4 cents at $3.51-1/2 per bushel. "We are hearing more and more yield reports that are above expectations ... This is giving more credibility to the USDA yield estimates on both corn and soybeans," Karl Setzer, market analyst for the Iowa-based MaxYield Cooperative, wrote in a note to clients. Futures drew underlying support from the USDA's confirmation that private exporters sold 597,464 tonnes of U.S. corn to Mexico and 132,000 tonnes of U.S. soybeans to China.

However, export sales commitments of both commodities are running behind year-ago levels. "The attitude is that supply is overshadowing demand," said Tom Fritz, a partner at EFG Group in Chicago. After the CBOT close, brokerage INTL FCStone raised its estimate of the U.S. 2017 corn yield to 169.2 bushels per acre (bpa), from 166.9 bpa in its previous monthly report released Aug. 31. The firm also raised its forecast of the U.S. 2017 soybean yield to 49.9 bpa, from 49.8 bpa previously.

The USDA said the U.S. soybean harvest was 22 percent complete by Sunday, behind an average of trade estimates for 25 percent and the five-year average of 26 percent.

The corn harvest was only 17 percent complete, lagging the five-year average of 26 percent. CBOT December wheat ended down 3-1/2 cents at $4.44-3/4 a bushel after dipping to $4.39-1/2, its lowest since Sept. 19. Spring wheat futures on the Minneapolis Grain Exchange fell even harder. The spot contract ended down 12-1/4 cents at $6.11-1/2 after sliding to $6.06, its lowest since mid-June, at the start of a summer drought that briefly lifted the market above $8 in July. The USDA on Friday reported U.S. 2017 production of spring wheat other than durum at 416 million bushels, up from its previous estimate of 402 million bushels and well above analysts' estimates.

CBOT settlement prices:

Last Net Pct Volume

change change

CBOT wheat WZ7 444.75 -3.50 -0.8 73885 CBOT corn CZ7 351.50 -3.75 -1.1 171081 CBOT soybeans SX7 957.25 -11.00 -1.1 99000 CBOT soymeal SMZ7 313.60 -2.20 -0.7 37464 CBOT soyoil BOZ7 32.52 -0.30 -0.9 59914

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 Nigel Hunt in London and Naveen Thukral in Singapore; editing by Edmund Blair and G Crosse)