CHICAGO - U.S. corn futures hit a three-month low and soybeans neared a three-week bottom after China said it would impose additional tariffs on U.S. products including grains and soy, escalating the trade war between the world's top two economies.

On the Chicago Board of Trade, soybean futures posted the biggest declines. China is the world's top soybean buyer, and the trade row has hit the market hard. But corn pared losses by midsession and wheat futures turned higher.

As of 11:46 a.m. CDT (1646 GMT), CBOT November soybeans were down 13-1/4 cents at $8.55-1/2 per bushel after hitting $8.55, the contract's lowest since Aug. 5.

December corn was down 3-3/4 cents at $3.67-1/4 a bushel after dipping to $3.65-1/2, its lowest since May 13, while December wheat was up 2-1/4 cents at $4.74 a bushel.

All three markets fell immediately after China said announced retaliatory tariffs against about $75 billion worth of U.S. goods, including agricultural products.

But the impact on grains was seen as largely psychological, given that China already said this month it halted purchases of U.S. agricultural products.

"China is already buying zero (U.S.) soybeans; I don't know if increasing the tariffs is going to change anything," said Joe Vaclavik, president of Standard Grain, a brokerage and consulting firm.

"Today's announcement was more about reinforcing negative market sentiment - which it did - and about communicating to traders that we are far from an agreement with China," INTL FCStone chief commodities economist Arlan Suderman said in a client note.

Traders continued to monitor crop weather in the U.S. Midwest, where corn and soybean crops are behind in development following widespread spring planting delays.

Storms brought much-needed moisture to the Corn Belt this week, alleviating worries about emerging dryness. But forecasts called for cool temperatures over the next 10 days, at a time when crops could use a warm spell.

"I have questions about whether we are lacking the heat that we need to push these crops to maturity," Vaclavik said.

Traders awaited U.S. corn and soybean crop estimates from editors of the Pro Farmer newsletter, due shortly after Friday's CBOT close.

The four-day Pro Farmer Midwest Crop tour wrapped up late Thursday, with scouts projecting below-average crop potential in Iowa, the top U.S. corn state, and Minnesota, the No. 4 corn producer.

(Additional reporting by Gus Trompiz in Paris and Naveen Thukral in Singapore, Editing by Sherry Jacob-Phillips, David Goodman and David Gregorio)

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