CBOT December corn settled up 1-1/2 cents at $3.70-1/4 a bushel after dipping to $3.66-1/4, the contract's lowest since mid-May.

The May and July 2020 corn contracts set life-of-contract lows.

The US Department of Agriculture said private exporters sold 328,000 tonnes of US corn to Mexico for delivery in the 2019/20 marketing year that begins Sept. 1.

The US Energy Information Administration said weekly US output of corn-based ethanol fell to 1.02 million barrels per day, the smallest since April, while stocks fell to 23.37 million barrels.

The Pro Farmer Midwest Crop Tour showed corn yield potential in Nebraska higher than the three-year average, while the tour's yield forecast for Indiana was below average, as expected.

Ahead of Thursday's weekly US Department of Agriculture export sales report, analysts expected the government to report corn export sales of 250,000 to 1,000,000 tonnes (old and new crop years combined).