GRAINS-U.S. wheat slips on fears of Black Sea competition

* Wheat falls back from 2-week top, soy off 3-week high

* Strong Black Sea wheat exports offer stiff competition

* Soybean crop ratings stable but dry weather a concern

(Updates with European trading, changes byline/dateline) PARIS/SINGAPORE, Sept 6 (Reuters) - Chicago wheat futures slipped on Wednesday, falling for the first time in four sessions, as expectations of increased supply from the Black Sea region raised concerns of stiff competition for exports ahead. Soybeans fell after climbing to a three-week high in the previous session, with stable U.S. crop ratings in a weekly government report tempering concerns about dry weather in parts of the Midwest. Corn also edged lower despite a slight deterioration in U.S. crop conditions, with prices curbed by the start of corn harvesting in the northern hemisphere and chart resistance following a rebound over the past week. The Chicago Board of Trade most-active wheat futures was down 0.3 percent at $4.41-3/4 a bushel by 1215 GMT, after closing up 1 percent on Tuesday. "Black Sea wheat exports are doing well. Some Texas ports are shut but the hurricane did not cause much damage to wheat," said Phin Ziebell, agribusiness economist, National Australia Bank. "The bigger picture is that we have ample supplies." UkrAgroConsult raised its forecast for Ukraine's 2017-18 grain exports by 3.4 percent to 42.06 million tonnes on Tuesday, underpinned by a bigger than expected harvest. Private forecasters have also been raising their estimates for Russia's grain crop to well above the government's current forecast of 110 million tonnes, fueled by mounting expectations for a record wheat crop. Russia's Agriculture Minister Alexander Tkachev told the RIA news agency on Wednesday that his ministry had proposed state subsidies for grain supplies by rail to the exporting ports of Russia's southern regions. In the United States, disruptions and delays to U.S. wheat exports from Texas as a result of hurricane Harvey will persist for days, trade experts said on Tuesday. The expected arrival of hurricane Irma in the southeast of the United States next week could also hit some soybean and corn crops, although concerns were more focused on cotton and orange crops. In a weekly update released after the market close on Tuesday, the U.S. Department of Agriculture (USDA) rated 61 percent of the soybean crop as good-to-excellent, unchanged from the previous week. However, forecasts for dry weather across much of the Midwest for the next 10 days were underpinning soybean prices as the market awaited a further harvest indication from monthly USDA forecasts on Sept. 12. "Short-covering operations with the approach of the next USDA report and because of dry conditions in the Midwest are offering support to prices," consultancy Agritel said in a note. CBOT soybeans fell 0.1 percent to $9.67-1/2 a bushel, but held close to Tuesday's high of $9.73-1/2, which was the highest since Aug. 10. Corn was down 0.4 percent at $3.57-1/4 a bushel.

Prices at 1215 GMT

Last Change Pct End Ytd Pct Move 2016 Move CBOT wheat 441.75 -1.25 -0.28 408.00 8.27 CBOT corn 357.25 -1.25 -0.35 352.00 1.49 CBOT soy 967.50 -1.00 -0.10 1004.00 -3.64 Paris wheat Dec 161.75 -0.75 -0.46 175.00 -7.57 Paris maize Nov 159.25 -0.75 -0.47 170.00 -6.32 Paris rape Nov 367.75 -2.25 -0.61 383.25 -4.04 WTI crude oil 49.21 0.55 1.13 53.72 -8.40 Euro/dlr 1.19 0.00 0.16

Most active contracts - Wheat, corn and soy US cents/bushel, Paris futures in euros per tonne

(Reporting by Naveen Thukral in Singapore and Gus Trompiz in Paris; editing by David Clarke)