KANSAS CITY (Dow Jones)--Chicago Mercantile Exchange lean hog and pork belly futures fell sharply Monday, pressured by uncertainty about demand, broken chart support levels and spreading.

In the other markets, live cattle and feeder cattle also were lower.

Lean hog futures tumbled to one-week lows in the most active October and December contracts. Losses in most contracts ranged from 1% to nearly 3%.

Concerns about a possible further slowing of pork export sales and seasonally larger hog supplies in the weeks ahead added to the pressure. A U.S. trade rift with China could limit sales of all meats and extend the ban initiated by that nation on imports of U.S. pork after the discovery of novel H1N1 influenza in Mexico and the U.S. in late April.

Flat-to-weaker cash market reports at midday along with lower wholesale pork prices Friday contributed to the slide. Lower corn prices also weighed on deferred hogs as cheaper feed costs may encourage some hog producers to maintain the size of their herds.

The final day of the official "Goldman roll" period, in which funds are shifting long positions out of October and into December, pressured the front month. The roll is in association with the S&P's GSCI.

October lean hogs closed down 152 points, or 2.9%, at 50.95 cents a pound. Most-active December hogs fell 82 points to 49.00 cents.

February pork bellies, the only contract traded, followed lean hogs down and fell 130 points to 87.00 cents.

Cattle Complex

Live cattle futures ended weaker on spread-trading, lower corn prices, and technical weakness.

Cash cattle sales last week at mostly steady prices were considered somewhat disappointing in terms of volume of animals sold overall and price after some traders had been expecting higher cash prices last week. Some traders are also concerned about demand for beef overall following the Labor Day holiday week amid competition from pork and chicken.

December cattle hit a one-week low, while front-month October matched Friday's low near 10-day moving average support.

Feeder cattle were modestly lower even though grains prices were down as well.

The October live cattle contract ended 17 points lower at 87.05 cents a pound. December was off 25 points at 86.67 cents. September feeder cattle were down 32 points at 98.85 cents, and October was down 40 at 98.92.

-By Curt Thacker, Dow Jones Newswires; 913-322-5178; curt.thacker@dowjones.com