GRAINS-Soybeans end lower in retreat from early strength

* Soybeans turn down after failing to match Thursday's peak

* Corn drifts lower as market awaits U.S. harvest news

* Wheat sags after 1-month top; Egypt tender results awaited

(Recasts; updates with closing prices, USDA crop progress data) CHICAGO, Sept 18 (Reuters) - U.S. soybean futures closed lower on Monday as a bout of technical selling erased early strength tied to export demand and uncertainty about Midwest yield prospects, analysts said. Corn fell on expectations of continued, burdensome U.S. supplies, and wheat also declined in listless trade. CBOT November soybeans settled down 1 cent at $9.67-3/4 per bushel. December corn ended down 3-1/4 cents at $3.51-1/2 a bushel and December wheat fell 5-1/2 cents to $4.43-1/2 a bushel. Soybeans turned down after the November contract for a second straight session failed to match or surpass Thursday's one-month high of $9.78-1/4 a bushel. Additional pressure stemmed from declines in CBOT soyoil futures that appeared to be tied to fund long liquidation. "Funds are long 100,000 contracts in bean oil, at the wrong time of year," said Mark Gold, managing partner at Top Third Ag Marketing. Soybean futures had climbed to session highs after the U.S. Department of Agriculture (USDA) through its daily reporting system said private exporters sold a total of 387,000 tonnes of U.S. soybeans, including 261,000 tonnes to China, the world's top soy buyer. "Export shipments through the first two weeks of the marketing year already exceed the seasonal pace needed to reach USDA's target by 45 million bushels. Said another way, we have to produce a big crop to keep up with this demand," INTL FCStone chief commodity economist Arlan Suderman said in a note to clients. U.S. and global supplies of corn, on the other hand, should remain ample. The USDA last week forecast a U.S. corn yield of 169.9 bushes per acre and 2017-18 ending stocks at a hefty 2.3 billion bushels. That factor weighed on CBOT corn futures. After the CBOT close, the USDA said the U.S. corn harvest was 7 percent complete, behind the five-year average of 11 percent. The government said the soybean harvest was 4 percent complete. Like soybeans, CBOT wheat futures closed lower in a reversal from early strength. The CBOT December contract turned lower on a lack of follow-through buying after reaching a one-month high at $4.50-3/4 a bushel. After the close, Egypt's General Authority for Supply Commodities set a tender to buy an unspecified amount of wheat from global suppliers for shipment from Oct. 21-31. Results were expected on Tuesday.

CBOT settlement prices:

Net Pct Volume

Last change change

CBOT wheat WZ7 443.50 -5.50 -1.2 51347 CBOT corn CZ7 351.50 -3.25 -0.9 99550 CBOT soybeans SX7 967.75 -1.00 -0.1 93991 CBOT soymeal SMZ7 312.60 1.20 0.4 41783 CBOT soyoil BOZ7 34.43 -0.38 -1.1 51320

NOTE: CBOT December wheat and 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 G Crosse and Jonathan Oatis)