GRAINS-Soy climbs to 3-week high on South America weather threats

* Soy up 1 percent on good global demand, weather worries

* Wheat rises on first sale to Egypt's state-buyer since April

* Weak dollar and firm crude oil support grain markets

(Updates prices, adds quotes, details) CHICAGO, Dec 3 (Reuters) - U.S. soybean futures rose 1 percent to a three-week high on Monday on robust demand from top importer China and adverse weather threatening production in Argentina and southern Brazil, two of the world's biggest suppliers. Wheat futures rebounded from a steep decline in the previous session when Egypt's state buyer booked its first U.S. wheat purchase since April, boosting hopes for more export business. Corn tracked wheat and soy higher, but gains were restricted demand from livestock feeders. A weaker U.S. dollar underpinned grains markets in general. The dollar index dipped to a one-month low as signs of progress in tackling Greece's debt lifted the euro, making dollar-denominated grains more attractive to overseas buyers.

Soybeans advanced because of traders' concerns that overly wet weather in No. 3 exporter Argentina and persistently dry conditions in southern areas of Brazil, the world's largest supplier after the United States, would trim production at a time when global supplies were uncomfortably tight. "The weather in South America is now front and center. There's been a less-than-ideal start to planting and the market is building back in a weather premium after that really sharp selloff we saw in soybean futures in November," said Brian Basting, commodity research analyst with Advance Trading. Brazil was still expected to harvest a record-large crop next year amid ideal weather in central Brazil, but dryness in the south could limit the crop's potential, analysts said on Monday. Rains in Argentina this week may sustain flooding that has swamped some areas of the grain belt and delayed planting.

STRONG DEMAND Meanwhile, robust demand from top importer China and from domestic U.S. processors, who have seen rising demand for soymeal and soyoil in recent weeks, further supported futures. Karl Setzer, a commodity trading advisor and market analyst with MaxYield Cooperative in West Bend, Iowa, said: "Crush is running high and our exports are high and the United States is the only source right now in the global market." Chicago Board of Trade January soybeans rose 14 cents, or 1 percent, to $14.52-3/4 per bushel by 11:50 a.m. CST (1750 GMT), briefly rising above its 200-day moving average of $14.62-1/4 before slipping back. Corn futures retreated from early gains as sluggish exports limited buying interest. CBOT March futures added just 1/4 cent to $7.53 a bushel. The U.S. Department of Agriculture on Monday said only 9.6 million bushels of corn were inspected for export last week, just a quarter of the total in the same week a year earlier and season-to-date shipments were only half of last year's pace. "In the first quarter of the marketing year, (corn) shipments were barely 200 million bushels. In a good year we get that in three or four weeks," said Basting, the Advance Trading analyst.

WHEAT REBOUNDS CBOT March wheat rose 1-1/2 cents, or 0.2 percent, to $8.65 per bushel after shedding 2.5 percent on Friday. Wheat climbed for the first time in three sessions as U.S. wheat claimed the bulk of a 400,000 tonne purchase by Egyptian government buyer GASC in a weekend tender. The market has anticipated for some time an upturn in U.S. wheat exports after weather-related supply snags in rival exporters like Russia and Argentina, as well as tight stocks in the European Union. Offers in the Egyptian tender showed the U.S. was now matching EU prices, even including higher shipping costs. "Wheat was sold off quite hard on Friday night on long liquidation and I think we are seeing a bit of correction today," Andrew Woodhouse, grains analyst at Advance Trading Australasia said.

Prices at 11:51 a.m. CST (1750 GMT)

LAST NET PCT YTD CHG CHG CHG CBOT corn 748.00 0.00 0.0% 15.7% CBOT soy 1452.75 14.00 1.0% 21.2% CBOT meal 445.70 3.30 0.8% 44.1% CBOT soyoil 50.01 0.60 1.2% -4.0% CBOT wheat 846.50 1.75 0.2% 29.7% CBOT rice 1532.00 5.00 0.3% 4.9% EU wheat 269.00 -0.50 -0.2% 32.8%US crude 89.29 0.38 0.4% -9.7% Dow Jones 13,006 -20 -0.2% 6.5% Gold 1717.04 2.15 0.1% 9.8% Euro/dollar 1.3057 0.0071 0.5% 0.9% Dollar Index 79.8640 -0.2890 -0.4% -0.4% Baltic Freight 1077 -9 -0.8% -38.0%

(Additional reporting by Gus Trompiz and Valerie Parent in Paris, Colin Packham in Sydney; Editing by Marguerita Choy and Grant McCool)