U.S. corn futures are expected to open lower Friday as worries about the global economy continues to batter commodities generally.

Chicago Board of Trade futures are expected to open 4 to 6 cents lower. In overnight trade, corn for December delivery was down 7 1/4 cents to $6.42 3/4.

Early gains in the overnight session, following Thursday's 5% plunge, evaporated late as European markets again swooned, analysts said. Worries about the global economy is sending traders fleeing from riskier assets and could also hurt demand for corn and other commodities. Sharply lower U.S. equities have added to the negative tone.

Corn has seasonal pressure as well, as the ongoing harvest pushes more supply into the pipeline, said Don Roose, president of U.S. Commodities in Des Moines, Iowa.

The December contract is down 15.4% since Aug. 30, and losses have been exacerbated as the market fell below technical support levels, which have prompted more liquidation, traders said. Front-month corn prices have not been this low in almost three months.

Longer-term, some analysts say corn's supply and demand fundamentals remain supportive. The government projects supplies will remain uncomfortably tight through next year, and this year's crop is expected to be a disappointment.

Traders say the U.S. Department of Agriculture has been counting on high prices to choke off, or "ration" demand, but with the recent sharp break in prices, some buyers are seeing an opportunity.

"We've got end-users covering stuff 6 to 8 months out," Roose said. "So there goes your rationing theory."

Still, MF Global broker Doug Bergman said that while signs of new demand are somewhat supportive, "more liquidation may need to take place before we stabilize."

Traders will be awaiting a Friday mid-morning report from a private analytical firm on planted acreage projections. The report is expected to be released around 11:30 a.m. CDT.