U.S. corn was little changed on Tuesday, holding at a one-month low on favorable supply prospects and a cautious mood in the run-up to closely watched U.S. government crop forecasts.

Wheat trading was also cautious after the market fell sharply on Monday along with corn, while soybeans edged higher.

An above-average pace of corn and soybean planting and improving wheat crop conditions shown by weekly U.S. Department of Agriculture (USDA) data late on Monday helped keep prices in check.

After investors squared some positions in the previous session following a rally linked to adverse weather in South America, activity was subdued ahead of the USDA's May supply and demand report due at 1600 GMT.

The most active corn futures on the Chicago Board of Trade inched down 0.3 percent to $3.68 a bushel by 1029 GMT, a lowest since April 13. On Monday, prices closed down more than 2 percent.

Analysts surveyed by Reuters expect the USDA to project that U.S. corn stocks will balloon above 2.2 billion bushels by the end of 2016/17, which would be the most since 1987/88.

"The market is expecting a bearish USDA report and that triggered the losses on Monday," said Andrew Woodhouse, grains analyst at Advance Trading Australasia.

The USDA report will include the government's first official supply-and-demand tables for the 2016/17 marketing year, drawing extra attention to the publication.

In wheat, the USDA already projects world wheat stocks to reach an all-time high by the end of 2015/16, and analysts expect stocks to swell further by the end of 2016/17.

The agency will also update its outlook for the current 2015/16 season, with attention on South American crops.

"We might get some surprises from USDA after the weather problems with Brazilian corn and Argentine soybeans," a European trader said.

The most active wheat futures was unchanged on the day at $4.56-1/2 a bushel, having closed down 1.6 percent on Monday.

The most active soybean futures rose 0.3 percent to $10.29-3/4 a bushel, having closed down 0.8 percent on Monday.

In its weekly crop progress report released after the market close on Monday, the USDA said U.S. corn plantings were 64 percent complete, above an average trade estimate of 62 percent.

Soybean planting progress was pegged at 23 percent complete, slightly ahead of expectations, while the winter wheat crop was rated 62 percent good to excellent, in line with expectations.