GRAINS-Soybeans approach 10-yr low as U.S.-China trade row escalates

* Soybeans fall to lowest since December 2008

* Corn futures set contract lows

* U.S.-China trade tension may hit U.S. bean exports

* Wheat down as U.S. winter crop harvest expands

(Recasts; updates prices, adds quotes, changes dateline; previous HAMBURG) CHICAGO, June 19 (Reuters) - U.S. soybean futures plunged on Tuesday to their lowest level in nearly a decade as escalating trade tensions between the United States and China, the world's biggest soy buyer, prompted fund-driven selling, analysts said. Corn and wheat followed broad declines in the commodity sector. Favorable weather in the Midwest bolstered corn and soy crop prospects, adding to bearish sentiment. As of 10:50 a.m. CDT (1550 GMT), Chicago Board of Trade July soybeans were down 29-1/2 cents at $8.79 per bushel after dipping to $8.41-1/2, the lowest spot price on a continuous chart since December 2008. CBOT July corn was down 5 cents at $3.51 after hitting $3.38-3/4, a contract low. CBOT July soft red winter wheat was down 11 cents at $4.79 a bushel after falling to $4.67-1/2, its lowest since April 4. Soybeans led the way down after U.S. President Donald Trump threatened to impose a 10 percent tariff on another $200 billion of Chinese goods. China's commerce ministry described the threat as "blackmailing" and said Beijing would fight back with "qualitative" and "quantitative" measures. "It's now a headline market," said Dan Basse, president of AgResource Co. "I can look at my economics all I want, and it doesn't do any good. It all comes down to what the big man wants to do with China," Basse said, referring to Trump. "I don't know how the markets sort through it other than the longs who have got margin calls are saying, 'I've had enough,"' Basse added. Additional pressure on corn and soybean prices came from crop-friendly weather across the U.S. Midwest. The U.S. Department of Agriculture (USDA) late on Monday rated 78 percent of the U.S. corn crop in good to excellent condition, up 1 percentage point from a week earlier. The rating was among the highest for this point in the season in USDA records dating back to the 1980s. The USDA rated 73 percent of the soybean crop as good to excellent, down from 74 percent the previous week, but still unusually high. CBOT wheat faced seasonal harvest pressure, with the USDA reporting the winter wheat harvest as 27 percent complete, ahead of the five-year average of 19 percent. However, analysts said trade tensions were the overriding issue in all grain markets.

CBOT prices as of 10:51 a.m. CDT (1551 GMT):

Net Pct Volume

Last change change

CBOT wheat WN8 479.00 -11.00 -2.2 71865 CBOT corn CN8 350.25 -5.75 -1.6 213189 CBOT soybeans SN8 881.75 -26.75 -2.9 128184 CBOT soymeal SMN8 333.00 -2.50 -0.8 65020 CBOT soyoil BON8 28.97 -0.60 -2.0 87871

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

(Additional reporting by Michael Hogan in Hamburg and Naveen Thukral in Singapore; Editing by Mark Potter and Dan Grebler)