Soybeans and corn hit four-year lows on US crop prospects

* Rising supplies and dismal demand keep prices under pressure

* Wheat futures fall almost 1%

(Adds European trade, new comment, changes dateline)

SINGAPORE/HAMBURG, Aug 12 (Reuters) - Chicago soybeans and corn futures fell on Monday to four-year lows below those hit the previous week, dropping below $10 and $4 a bushel respectively ahead of a U.S. government report expected to forecast bigger U.S crops.

Wheat fell more than 1%, with cheap Black Sea supplies expected to dominate a massive 3.8 million metric ton purchase tender from Egypt.

"There is a lot of bearishness in corn and soybean markets on expectations of higher U.S. output and overall global supplies," said one Singapore-based trader.

The Chicago Board of Trade's most active soybean contract fell 0.5% to $9.97-3/4 a bushel by 0921 GMT and corn fell 0.3% to $3.93-3/4 a bushel, both at their lowest since late 2020.

Wheat was down 0.9% at $5.37-1/4 a bushel.

The U.S. Department of Agriculture's (USDA) monthly world agricultural supply and demand crop estimates due later on Monday are forecast to show larger U.S. harvests of soybeans, corn and wheat, analysts say. This will add to large global supplies while demand remains slack.

Wheat traders were awaiting news of price offers in Egypt’s enormous wheat tender, expected to be disclosed later on Monday.

“Russian and other Black Sea prices are currently so low, around $20 cheaper than western Europe, that they are likely to win the Egyptian business,” one German trader said. “There is not much optimism other origins are in with a chance.”

Ukrainian wheat is even cheaper than Russian and the tender could provide another boost to strong Ukrainian grain exports, traders said, though the 270-day payment delay offered by GASC could discourage some from participating.

Wheat’s fall was limited by bad crop news from France and elsewhere in Europe.

France's 2024 soft wheat crop is expected to be 25% below last year's after relentless rain. (Reporting by Naveen Thukral in Singapore and Michael Hogan in Hamburg Editing by Sherry Jacob-Phillips, Rashmi Aich and David Goodman)