GRAINS-Soybeans extend gains on South America weather worries

* Soybeans up at highest since Dec. 12 on Argentina dryness

* Rain delays in Brazilian harvest could boost U.S. exports

* Corn firm on South America, big weekly U.S. exports

* Wheat higher after falling Friday on weak exports

(Updates with European trading, changes byline/dateline) PARIS/SINGAPORE, Jan 22 (Reuters) - Chicago soybeans rose for a sixth straight session on Monday to reach their highest in almost six weeks as weather threats to South American crops continued to fuel buying. Corn edged up, supported by strong weekly U.S. export figures and the weather risks in South America, while wheat also rose. The most-active soybean contract on the Chicago Board of Trade was up 0.8 percent at $9.84-3/4 a bushel as of 1129 GMT, after earlier touching its highest since Dec. 12 at $9.85 a bushel. Weather concerns are focused on persistent dryness in Argentina, the world's third-largest producer of the oilseed and the biggest exporter of soymeal livestock feed. CBOT soymeal also notched up a sixth consecutive gain to hit a new six-week high of $335.70 per ton. "The soybean market responded (to dryness in Argentina) by adding to the weather premium in prices," said Tobin Gorey, director of agricultural strategy, Commonwealth Bank of Australia. "The weather premium is now large enough to have lifted Chicago March soybeans out of their range for the past month." The Buenos Aires Grain Exchange said last week it could reduce its 2017/18 soybean planting area estimate further after sowing delays caused by dry weather in northwestern Argentina.

High temperatures since the weekend have added to the prospect of fields drying out further amid only light rain in Argentina's main grain belts. "Concerns over corn and soybean yields in Argentina return to the forefront as dry weather sets up once again," Thomson Reuters Agriculture Research analysts said in a note. "Cooler temperatures, however, will mitigate loss to yield potential." Meanwhile, wet weather in Brazil has slowed the start of the soybean harvest there, which should result in a sharp reduction in the amount of soy that available in the market by the end of January. This could lead to extra demand for U.S. supplies, on top of bigger than expected weekly export sales of 1.528 million tonnes reported by the U.S. Department of Agriculture on Friday.

CBOT corn gained 0.4 percent to $3.54 a bushel, after earlier reaching its highest in nearly three weeks at $3.54-1/2. Wheat rose 1.0 percent to $4.26-3/4 a bushel to recoup Friday's fall. Weekly corn export sales of 1.891 million tonnes were well above analyst estimates. But export sales of wheat were just 190,500 tonnes, below a range of market forecasts, contributing to Friday's drop in CBOT wheat.

Prices at 1129 GMT

Last Change Pct End Ytd Pct Move 2017 Move CBOT wheat 426.75 4.00 0.95 427.00 -0.06 CBOT corn 354.00 1.50 0.43 350.75 0.93 CBOT soy 984.75 7.50 0.77 961.75 2.39 Paris wheat Mar 155.50 0.25 0.16 159.00 -2.20 Paris maize Mar 152.50 0.50 0.33 157.75 -3.33 Paris rape Feb 346.50 1.00 0.29 347.75 -0.36 WTI crude oil 63.40 0.03 0.05 60.42 4.93 Euro/dlr 1.23 0.00 0.30

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 Sherry Jacob-Phillips and Edmund Blair)