CANBERRA, March 27 (Reuters) - Chicago wheat futures fell towards 3-1/2-year lows on Wednesday as traders dismissed concerns that exports from top supplier Russia would be disrupted and focused instead on a plentiful supply outlook.

Soybean and corn futures also fell as the markets looked ahead to data on U.S. planting and grain stocks due on Thursday that could move prices.

The most-active wheat contract on the Chicago Board of Trade (CBOT) was down 0.8% at $5.39-1/4 a bushel by 0428 GMT, while CBOT soybeans fell 0.6% to $11.92 a bushel and corn slipped 0.8% to $4.29 a bushel.

All three crops are well supplied and the contracts are near their lowest levels since 2020, with speculators betting heavily on further declines.

Huge amounts of cheap wheat are emerging from Russia, which expects a third consecutive large harvest this year and could set a new March shipping record of 5 million tons this month.

Ample supply is pulling prices lower and some traders expect the U.S. Department of Agriculture (USDA) to reveal a rise in inventories later this week, said Rod Baker at Australian Crop Forecasters.

Wheat advanced to $5.67 on Monday, the highest levels since March 4, as a dispute between Russian authorities and a leading export company held up shipments.

Also creating supply concerns were Russian attacks on infrastructure in Ukraine, another large grain exporter, and Russian accusations that Kyiv helped arrange a terror attack in Moscow, but these worries have faded.

Commodity funds were net sellers of CBOT corn, soybean and wheat futures contracts on Tuesday, traders said.

Elsewhere, soft wheat exports from Europe were slightly down on last year's pace and soybean imports into Europe were roughly unchanged from last year, EU data showed.

Ahead of a U.S. planting report on Thursday, grain market analysts predict U.S. corn and wheat plantings will fall in favour of soybeans.

In Brazil, consultancy hEDGEpoint lowered its forecast for the nation's 2023-24 corn crop to 119.1 million metric tons from 121.5 million tons.

Brazil's soybean exports are expected to reach 13.49 million metric tons this month, grain exporters lobby group Anec said.

South African farmers are expected to harvest 13.26 million metric tons of maize (corn) in 2024, down from 16.43 million the season before, the government's Crop Estimates Committee (CEC) said.

(Reporting by Peter Hobson; Editing by Sherry Jacob-Phillips and Mrigank Dhaniwala)