GRAINS-Soybeans ease before USDA data, canola slides on China anti-dumping duty

By Gus Trompiz and Naveen Thukral

PARIS/SINGAPORE, Aug 12 (Reuters) - Chicago soybeans eased on Tuesday, giving up some of Monday's gains as hopes of renewed Chinese demand cooled, while Canadian canola plunged 6% after China announced a steep anti-dumping duty.

Corn and wheat also eased as traders adjusted positions before the monthly U.S. Department of Agriculture supply and demand report at 1600 GMT, which is expected to show plentiful U.S. and global supplies.

The most-active soybean contract on the Chicago Board of Trade (CBOT) Sv1 ended the overnight trading session down 1.3% at $9.98-1/4 a bushel, edging back below the $10 threshold crossed during Monday's 2.4% rally.

The day-earlier gains came after U.S. President Donald Trump urged China, the world's biggest soybean importer, to quadruple its purchases of U.S. beans.

Washington and China later announced they were extending a tariff truce for a further 90 days, but there was no immediate agreement on agricultural trade.

"No confirmation (or) comments from China afterwards, just the silent extension of the 90-day tariff truce by the U.S., and beans are down today as well as U.S. grains," Andrey Sizov, head of agricultural consultancy Sovecon, said.

China has refrained from forward purchases of the upcoming U.S. crop, reinforcing Brazil's position as its main soybean supplier.

November canola futures RSX5 on ICE were down 6.4% at C$637.00 ($462.36) a metric ton after falling to a four-month low of C$636.30 to approach its daily trading limit.

China on Tuesday announced a preliminary anti-dumping duty of 75.8% on Canadian canola imports, a fresh escalation in a year-long trade dispute that began with Ottawa's imposition of tariffs on Chinese electric vehicle imports.

Traders are watching to see if China opens its market to Australian canola, previously banned due to crop disease concerns, though they said it may be difficult to entirely replace Canadian supply, which dominates China's canola imports.

CBOT corn Cv1 lost 0.8% to $4.04-1/2 a bushel, while CBOT wheat Wv1 shed 1.3% to $5.08-1/4 a bushel.

Condition ratings for U.S. corn and soybean crops eased in a weekly USDA report on Monday in line with market expectations, but the corn score remained at a nine-year high.

Tuesday's USDA report will give a pointer to yield potential for the autumn harvest.

"The August (report) often is a big market-moving report," Sizov said. "It feels that very optimistic (corn) expectations are largely priced in already, which could lead to a spike if USDA's number is modest."

($1 = 1.3777 Canadian dollars)