GRAINS-Corn and soybeans slide on U.S. crop weather, trade jitters

* Analysts expect strong USDA corn and soy crop ratings

* U.S.-China trade doubts hang over grain markets

* Wheat pressured as U.S. winter wheat harvest begins

(Recasts, updates prices, adds quotes, changes byline, changes dateline from PARIS/SINGAPORE) CHICAGO, June 4 (Reuters) - U.S. corn futures fell more than 2 percent on Monday, the biggest single-day slide for the most-active contract in six weeks, on favorable U.S. crop weather and escalating trade tensions, analysts said. Soybeans and wheat followed the weak trend that spread across commodity markets. As of 12:45 p.m. CDT (1745 GMT), Chicago Board of Trade July corn was down 10-1/4 cents at $3.81-1/4 per bushel, testing chart support at its 200-day moving average. CBOT July soybeans were down 18-1/2 cents at $10.02-3/4 a bushel and wheat was down 17-3/4 cents at $5.05-1/2 a bushel. Analysts expected the U.S. Department of Agriculture's weekly crop progress report later on Monday to show strong condition ratings for corn and soybeans, underscoring that both crops are off to a good start in the U.S. Midwest. "The crop is nearly planted. The ratings are high. The weather pattern is rather progressive, with regular showers coming along," said Rich Feltes, vice president for research with R.J. O'Brien. Recent spells of hot weather were not a concern, Feltes said. "This time of year, the warm temperatures are favorable, pushing the (corn) crop along, setting the table to have earlier pollination," he said. Worries about U.S. trade relations with China, the world's top soy importer, also hung over the market. The two countries ended their latest round of negotiations on Sunday with U.S. Commerce Secretary Wilbur Ross and his delegation leaving Beijing without making a public statement. China also made no mention of any new agreements. "Against a backdrop of good crop conditions, this trade uncertainty is piling on to all the other negative news," Feltes said. Wheat also gave up ground, with the spot CBOT contract falling 3 percent to its lowest in nearly two weeks as harvest progress in the southern U.S. Plains shifted attention away from dry weather risks in Australia and the Black Sea region. The USDA planned to release its first estimates of U.S. 2018 winter wheat harvest progress later on Monday, and analysts expected the government to show the national harvest as 8 percent complete. "We estimate that 20 percent of Oklahoma has been cut, but the next week should see significant progress because yields are generally low and abandonment high in the state," INTL FCStone chief commodities economist Arlan Suderman wrote in a client note.

CBOT prices as of 12:45 p.m. CDT (1745 GMT):

Net Pct Volume

Last change change

CBOT wheat WN8 505.75 -17.50 -3.3 76812 CBOT corn CN8 381.25 -10.25 -2.6 198190 CBOT soybeans SN8 1003.50 -17.75 -1.7 75208 CBOT soymeal SMN8 369.70 -4.50 -1.2 42929 CBOT soyoil BON8 30.97 -0.22 -0.7 56181

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 Gus Trompiz in Paris and Naveen Thukral in Singapore Editing by Susan Thomas)