* Ample wheat supplies for Northern Hemisphere harvest weigh

* CBOT soybean futures hit lowest in four years, corn down

SINGAPORE, July 15 (Reuters) - Chicago wheat lost more ground on Monday, with prices dropping to their lowest levels in three-and-half months, as pressure from freshly-harvested crops in the United States and Russia dragged down the market.

Soybeans dropped to their lowest levels in four years, while corn fell on expectations ample global supplies.

"U.S. wheat harvest in nearly done and Russian weather is good for harvest to progress," said one Singapore-based trader. "We have seen pretty big drop in prices as supplies are rising."

The most-active wheat contract in the Chicago Board of Trade (CBOT) lost 1.3% to $5.43-3/4 a bushel as of 0334 GMT, after dropping to its lowest since April 3 at $5.41-3/4 a bushel earlier in the session.

Corn gave up 0.8% to $4.11-1/2 a bushel and soybeans slid 1.1% to $10.53-1/2 a bushel, after falling to their lowest since 2020 at $10.52 a bushel earlier on Monday.

Wheat prices have been weighed down by warm and dry weather, which is boosting harvest in key Northern Hemisphere suppliers.

The U.S. Department of Agriculture (USDA) on Friday raised its estimate for corn production and cut the soybean production forecast, adjusting its estimates in line with the amount of acres planted with each crop.

The USDA also predicted that the 2024/25 corn crop is poised to be the third-largest in U.S. history, with corn end-stocks being the largest in six years, as of September 2025.

Still, USDA estimated old-crop corn ending stocks would be 1.877 billion bushels, when traders had expected the USDA to set the number at 2.049 billion bushels.

Meanwhile, Ukraine's

grain exports in the 2024/25 marketing season rose to 1.5 million metric tons by July 12 from 894,000 tons a year earlier, agriculture ministry data showed on Friday.

Large speculators increased their net short position in CBOT corn futures in the week ended July 9, regulatory data released on Friday showed.

The Commodity Futures Trading Commission's weekly commitments of traders report also showed that non-commercial traders, a category that includes hedge funds, trimmed their net short position in CBOT wheat and increased their net short position in soybeans. (Reporting by Naveen Thukral; Editing by Sherry Jacob-Phillips and Varun H K)