GRAINS-Chicago soybeans rise on Argentina weather woes, corn flat

Updates at 0845 GMT

By Ella Cao and Mei Mei Chu

BEIJING, Feb 14 (Reuters) - Chicago soybean futures rose for a second session on Friday, underpinned by weather concerns in key supplier Argentina, although weak exports and progress in Brazilian harvest kept the market on track for a weekly decline.

Corn prices were poised for a second week of gains due to tighter global stocks, strong demand, and Argentina weather woes. Wheat was set for a sixth week of gains, supported by strong exports and freeze risks in key growing regions.

Soybeans Sv1 gained 0.19% to $10.32 per bushel by 0442 GMT, but were down 1.67% for the week. Corn Cv1 remained unchanged at $4.93 per bushel, but was up 1.18% for the week despite expectation of higher production in Brazil.

On Thursday, Brazil's crop agency Conab lowered its soybean supply forecast in the world's top supplier due to dry weather in the south, but raised corn estimates.

Argentina's dry conditions boosted soybean and corn prices, though rains have eased the dryness.

Weak Chinese demand and expectations of a bumper harvest in Brazil have weighed on soybean prices.

Weekly U.S. soybean exports were below expectations, while corn sales exceeded forecasts, according to a report from the U.S. Department of Agriculture (USDA) on Thursday.

The grain market remained cautious as traders awaited U.S. President Donald Trump's efforts to negotiate an end to the Ukraine war and updates on tariff changes with key trading partners.

Andrew Whitelaw, an analyst at Episode 3 in Canberra, said that while the Russian-Ukraine peace talks will impact the market, their effect on supply chains and agricultural production is still some time away.

If the sanctions against Russia end, it may be bearish for the European market as Russian products may re-enter the market, said Johnny Xiang, founder of Chinese consulting firm AgRader.

On Thursday, the U.S. moved to raise decades-old low tariff rates to match those of other countries, citing Brazil's ethanol tariffs as an example of unfair trade practices. Most of U.S. ethanol comes from corn.

"It absolutely will swing back demand to domestically produced ethanol rather than Brazilian imports due to the differential in tariffs if these tariffs become equal. But it's a wait and see," Whitelaw said.

Wheat Wv1 climbed 1.13% to $5.84 a bushel, extending weekly gains with a 0.26% rise, partly supported by Saudi Arabia's tender to buy an estimated 595,000 metric tons, analysts said.

Traders are monitoring cold fronts in the U.S. Plains and Black Sea for freeze risks, though snow forecasts may protect the crop.