GRAINS-Chicago soybeans retreat from one-month high on tariff uncertainty

By Ella Cao and Colleen Howe

BEIJING, April 2 (Reuters) - Chicago soybean futures declined on Wednesday, retreating from a one-month high hit in the previous session, as concerns over an upcoming tariff announcement threatened U.S. farm exports.

On Tuesday, gains were fuelled by a meeting between a coalition of oil and biofuel groups and the U.S. Environmental Protection Agency, which discussed raising federal mandates for biomass diesel blending, leading to higher soyoil prices.

As of 0301 GMT, the most-active soybean contract on the Chicago Board of Trade (CBOT) was down 0.27% at $10.32 a bushel.

Meanwhile, wheat extended gains for a third consecutive session, supported by concerns over U.S. supply and trade policy, according to traders.

The latest U.S. Department of Agriculture report projected lower-than-expected planting intentions.

Dry conditions across the Northern Plains heightened supply concerns, while the potential U.S. tariff on Canadian wheat imports could further tighten availability, said Cheang Kang Wei, assistant vice president at StoneX in Singapore.

"If the U.S. does not proceed with proposed ocean freight tariffs, additional upside momentum may emerge. The combination of reduced acreage, weather risks, and trade policies could make U.S. spring wheat particularly volatile in the coming months," Cheang said.

The most-active wheat contract Wv1 rose 0.05% to $5.41 a bushel.

Corn futures Cv1 slid 0.6% to $4.59 a bushel after three straight sessions of gains.

Despite this pullback, corn prices had been supported by wet weather forecasts for the U.S. Delta and Ohio Valley next week, which could delay planting.

Meanwhile, StoneX estimated Brazil's first corn crop at 25.90 million tons, down from a previous estimate of 26.53 million tons, while the second crop is now forecast to stand at 101.62 million tons, down from the initial outlook of 102.13 million tons.

Traders are closely monitoring the April 2 tariff announcement, along with concerns over proposed U.S. port fees on Chinese-built vessels.

According to the Washington Post on Tuesday, White House aides are proposing tariffs of about 20% on most U.S. imports.

Commodity funds were net buyers of Chicago Board of Trade soybean, soyoil, corn and wheat futures contracts on Tuesday and net sellers of soymeal futures contracts, traders said. COMFUND/CBT