GRAINS-Soybeans at 3-week low on ample supply; wheat, corn down

* Soybeans down on ample Latin American oilseed supplies

* Wheat down after peaking near 13-month high

* Corn further down on hopes sowings will speed up

(Updates prices, comments; changes byline/dateline) PARIS/SINGAPORE, May 6 (Reuters) - Chicago soybeans fell to a three-week low on Tuesday due to plentiful supplies in South America, slowing demand and rising stocks of rival oilseed canola. Wheat declined slightly after trading near its highest in more than 13 months in the previous session as political turmoil in major supplier Ukraine and dry weather in the U.S. Plains stoked global supply concerns. Corn edged lower, the fourth fall out of five sessions, on prospects that sowing will speed up. Chicago Board of Trade July soybeans fell 1.1 percent decline on Monday. July wheat fell 0.7 percent to $7.24 a bushel, having closed up 1.8 percent on Monday. The front-month contract fell 0.45 percent to $7.18 a bushel, after climbing on Monday to $7.32 a bushel, its highest since March 28 last year. July corn fell 0.6 percent to $5.04-3/4 a bushel. Analysts Informa Economics FNP said in its latest report released on Monday it expected Brazil's 2013/14 soybean crop, which is near the end of the harvest season, to be 87.4 million tonnes, up from the 86.75 million tonne forecast in April. If the estimate is accurate, it will be Brazil's largest ever and 5.9 million tonnes more than the current record harvest in 2012/2013. U.S. analysts expect the U.S. Department of Agriculture to raise its Argentine 2013/14 soybean crop estimate while slightly reducing the forecast for Brazil in its May crop report, due to be released on Friday, May 9. The USDA pegged export inspections of U.S. soybeans in the latest week at 99,502 tonnes, below a range of trade estimates for 100,000 to 200,000 tonnes, highlighting slowing demand. Canadian canola stocks have grown to an all-time high for this time of year, while wheat stocks are the biggest in 20 years, according to Statistics Canada estimates released on Monday, reflecting a record-breaking harvest and a backlog in moving crops by rail. Wheat fell back slightly as some traders closed their positions after a 10 percent rise in less that two weeks. Scorching temperatures in the southern U.S. Plains over the weekend stressed developing winter wheat crops, which have already endured months of drought, and relief is not expected until mid-week, forecasters said, fueling a rally in prices on Monday. Rising tensions in Ukraine, which led German Foreign Minister Frank-Walter Steinmeier to say the country was close to war, lent additional support to the wheat market.

Pro-Russian rebels shot down a Ukrainian helicopter in fierce fighting near the eastern town of Slaviansk on Monday, and Kiev drafted police special forces to the southwestern port city of Odessa to halt a feared westward spread of rebellion.

Corn fell slightly on hopes that improved weather in the corn belt could speed up sowings. Farmers had planted 29 percent of their corn crop as of May 4, up 10 percentage points from a week earlier, according to the USDA's weekly crop progress and condition report. That compares with the five-year average of 42 percent and analysts' expectations of 33 percent. "With the risk of planting delays severe enough to impact yields declining, we expect the risk premiums in new crop corn and soybean prices to erode further in the coming weeks," investment bank Morgan Stanley said in a market note.

Prices at 1041 GMT

Product Last Change Pct Move End 2013 Ytd


CBOT corn 504.75 -3.25 -0.64 437.00 15.50 CBOT soy 1446.75 -16.50 -1.13 1264.50 14.41 CBOT wheat 724.00 -5.00 -0.69 616.75 17.39 Paris wheat 206.75 -1.75 -0.84 190.50 8.53 Paris maize 184.75 -1.25 -0.67 171.75 7.57 Paris rape 351.75 -5.25 -1.47 366.50 -4.02 WTI crude oil 99.66 0.18 +0.18 91.82 8.54 Euro/dlr 1.39 +0.37 * CBOT futures prices are in cents per bushel, Paris futures

in euros per tonne, WTI crude oil in dollars per barrel.

(Editing by Jane Baird)