GRAINS-Soybeans hit 3-week high as Argentine weather worries return

* Unfinished Argentine soy sowing puts focus back on dryness

* Corn, wheat curbed by low weekly export sales

* Wheat still set for weekly gain on U.S. cold weather

(Updates with European trading, changes byline/dateline) PARIS/SINGAPORE, Jan 5 (Reuters) - U.S. soybean futures rose on Friday to reach a three-week high after a report pointing to the risk of unfulfilled plantings in Argentina which revived concerns about dry weather in the world's third-largest producer of the oilseed. Chicago wheat edged lower, partly pressure by weak export data, but was still set for a third positive week amid concerns that cold, dry weather may hurt U.S. wheat crops. Corn was little changed. The most-active Chicago Board of Trade soybean futures was up 0.3 percent at $9.70-1/2 a bushel by the end of the overnight trading session, after earlier reaching their highest since Dec. 14 at $9.77. Forecasts calling for widespread rain from the middle of next week in Argentina had curbed prices on Thursday, but an overnight report from the Buenos Aires Grains Exchange shifted attention back towards dry weather risks. The exchange said drought in Buenos Aires province could leave some of the 18.1 million hectares expected to be sown with soy this season unplanted, with 2.25 million hectares yet to be sown as the end of the planting window approaches. Weather forecasters also said that expected showers may not be enough to reverse dryness in some areas amid warm temperatures. "Relief likely for most Argentina corn/soy in week 2; highest risk for dry patches to linger in southern quarter," the Commodity Weather Group said in a daily update. The most-active CBOT wheat contract is down 0.8 percent at $4.30-3/4.

Wheat added to a marginal overnight loss after the U.S. Department of Agriculture (USDA) reported export sales of U.S. wheat of just 131,000 tonnes. This was well below market estimates although traders played down the significance of the figures which covered the Christmas holiday period. Wheat remained underpinned by fears that frigid temperatures caused damage this week to crops already struggling with persistent dry weather. Corn was down a quarter of a cent at $3.50-3/4 a bushel, with support from weather risks in Argentina offsetting modest weekly exports as with wheat.

Prices at 1403 GMT

Last Chang Pct End Ytd Pct e Move 2017 Move CBOT wheat 430.75 -3.25 -0.75 427.00 0.88 CBOT corn 350.75 -0.25 -0.07 350.75 0.00 CBOT soy 970.50 2.75 0.28 961.75 0.91 Paris wheat Mar 160.50 0.00 0.00 159.00 0.94 Paris maize Mar 158.25 3.75 2.43 157.75 0.32 Paris rape Feb 357.75 0.00 0.00 347.75 2.88 WTI crude oil 61.53 -0.48 -0.77 60.42 1.84 Euro/dlr 1.21 0.00 -0.14

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 Richard Pullin and Jane Merriman)