U.S. corn futures are expected to start firmer Wednesday on concerns farmers will not sow enough of the grain to rebuild low supplies.

Traders and analysts predict corn for May delivery, the most actively traded contract, will start 1 to 2 cents a bushel higher at the Chicago Board of Trade. In overnight electronic trading, the contract rose 1 1/4 cents, or 0.2%, to $6.73 a bushel.

Market participants are positioning themselves before the U.S. Department of Agriculture releases hotly anticipated estimates on crop plantings and grain inventories Thursday. An expected increase in corn plantings this spring may not be sufficient, as poor weather could reduce yields and season-end supplies are already projected to reach a 15-year low, analysts said.

"It is all about tomorrow's reports," said Duane Lowry, analyst for Early Market News, an agricultural advisory firm.

Gains heading into the reports would follow a 2.6% selloff in the market during the first two days of the week. It seems "prereport liquidation activity has been exhausted" amid ongoing concerns about supplies, Lowry said.

Corn futures earlier this month topped 2 1/2-year highs on strong demand and concerns farmers will not plant enough. The market has since retreated about 8.4% on profit-taking and fears about reduced global consumption.

Yet demand for the grain remains strong. Tyson Foods--the world's largest processor and marketer of chicken, beef and pork--used the recent break in corn prices to cover most of its feed needs through the summer, the company's chief operating officer said Wednesday.

Traders also continue to talk about the potential for major export sales to China, which was the suspected buyer of 1.25 million tons of corn in a sale to "unknown destinations" announced by the government Friday. China's Ministry of Finance is considering whether to adjust tariffs on imports of agricultural commodities, but hasn't made any decision yet, according to a report in the official Beijing Business Today. The USDA did not make fresh sales announcements Wednesday.

China also is interested in buying corn from Argentina, the world's second-largest exporter of the grain behind the U.S., traders said. Chinese food health officials are in Buenos Aires to discuss quality standards of Argentine corn, according to a research note from Australia & New Zealand Banking Group. It said the main issue being looked at was genetically modified varieties of Argentine corn, as China only allows specific strains into the country.