U.S. corn futures dropped to a fresh one-week low Monday, pressured by profit-taking as traders look to reduce risk ahead of crop reports from government forecasters.

Corn futures for May delivery fell 9 1/4 cents, or 1.4%, to $6.49 a bushel at the Chicago Board of Trade.

The declines were driven partly by managed funds selling futures to exit bets that prices would rise. Many market participants have taken more cautious positions ahead of supply and demand reports due out Tuesday from the U.S. Department of Agriculture.

The USDA will release updated U.S. and world supply and demand estimates Tuesday at 8:30 a.m. EDT. The general consensus of analysts calls for tighter U.S. and world supplies.

"While traders anticipate tighter supply forecasts, the inventory levels are still not to a point that would justify further rationing of demand beyond today's price levels," said Karl Setzer, analyst with MaxYield Cooperative in West Bend, Iowa.

Increased competition in the world market from other corn sources, including South America and Ukraine is a reflection that demand rationing is occurring, said Setzer.

Ukraine announced China bought corn and wheat from Ukraine. This marks the first time China has imported corn from the Eastern European nation, with the amount expected to reach between 1 million and 1.5 million tons within the next three years, Oleg Bakhmatyuk, chairman at Ukrlandfarming PLC said in a report.

Soybean futures ended lower, succumbing to profit-taking as well. "The market is terribly vulnerable to a downward price correction," said Anne Frick, senior oilseed analyst with Jefferies Bache in New York.

Traders are factoring in the risk that USDA may not issue anything bullish in the report Tuesday, Frick said. "Tighter supplies and strong demand are fundamentally bullish, but we have priced in all these factors and at some point, South American crop production estimates will stop going down," she added.

CBOT May soybeans dropped 3 cents to $14.31 a bushel.

The front months in both corn and soybeans led the way down, as index funds began rolling out of their spot positions.

There were also concerns over the state of the U.S. economy, mainly from the poor jobs report issued Friday. "Unemployment is not dropping as fast as thought in the U.S., contrary to recent spending reports," Setzer said.

Wheat futures ended mostly higher, drawing support from traders covering short positions ahead of Tuesday's crop reports. However, hard red winter wheat futures at KCBT fell on improved growing conditions for crops in the U.S. plains.

CBOT May wheat ended up 4 1/2 cents at $6.43 a bushel, May KCBT wheat ended 2 cents lower at $6.60 and May MGEX wheat ended up 1 cent at $8.47.

-By Andrew Johnson Jr, Dow Jones Newswires; 312-347-4604 begin_of_the_skype_highlighting 312-347-4604 end_of_the_skype_highlighting; Andrew.johnsonjr@dowjones.com