GRAINS-Wheat extends decline as Russian supply worries abate

* Russia's agriculture ministry raises grain crop forecast

* Softer Russian wheat prices add pressure

* Soybeans subdued as Trump cautious on China trade talks

* Corn weakened by wheat, good Midwest crop prospects

(Updates with closing U.S. prices) CHICAGO, Aug 21 (Reuters) - U.S. wheat futures fell on Tuesday for a second straight session as fears of a shortfall in Russian wheat exports diminished, traders said. Corn and soybean futures also declined, pressured by spillover weakness from wheat as well as improving crop conditions in the U.S. Midwest after widespread rains. Chicago Board of Trade December wheat futures settled down 14-3/4 cents at $5.47-3/4 per bushel. December corn ended down 2-1/4 cents at $3.74-1/4 a bushel and November soybeans fell 7-1/4 cents to $8.86 a bushel. Wheat led the way down as worries about tightening Russian supplies eased. Analysts noted a decline this week in Russian wheat export prices, as well as softening values for Ukrainian and French wheat. "It looks to me like the wheat market just got ahead of itself," said Jim Gerlach, president of Indiana-based A/C Trading. "You've got the largest net long (position) for managed money since 2012 ... And Russian wheat export prices have been down for two weeks in a row," Gerlach said. Speculation about potential export limits in Russia, the world's biggest wheat supplier, pushed global wheat prices sharply higher on Friday, adding to worries about tightening global supplies following drought in Europe, the Black Sea region and Australia. But Russia's agriculture minister does not currently see any reason to introduce an export duty on wheat, the RIA news agency reported on Tuesday. Also, the agriculture ministry raised its forecast for the country's 2018 grain crop to between 100 million and 105 million tonnes, from 100 million previously. "Russia denies it is impeding wheat exports so the market, for now, relaxes," said Tobin Gorey, director of agricultural strategy at Commonwealth Bank of Australia. CBOT corn and soybean futures followed the weak trend as beneficial rains across the Midwest this week bolstered U.S. crop prospects. Yield prospects for corn and soybean crops in South Dakota and Ohio are up from a year ago and above average, scouts on an annual U.S. crop tour found on Monday.

The Pro Farmer Midwest Crop Tour was expected to release yield estimates for Nebraska and Indiana later on Tuesday. CBOT soybean futures drew additional pressure from doubts about whether trade talks this week between top global soy buyer China and the United State would ease tensions. U.S. President Donald Trump told Reuters on Monday he did not expect much progress from the talks in Washington. A standoff has seen Beijing put extra tariffs on U.S. soybeans, slowing shipments of American supplies to the world's biggest importer of the oilseed.

CBOT settlement prices:

Net Pct Volume

Last change change

CBOT wheat WZ8 547.75 -14.75 -2.6 69596 CBOT corn CZ8 374.25 -2.25 -0.6 127309 CBOT soybeans SX8 886.00 -7.25 -0.8 75308 CBOT soymeal SMZ8 327.20 -3.40 -1.0 33672 CBOT soyoil BOZ8 28.95 0.07 0.2 39123

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 Gus Trompiz in Paris and Naveen Thukral in Singapore; Editing by James Dalgleish and Tom Brown)