Copper prices were rallying Thursday on worries that supplies wouldn't be enough to meet demand.

Benchmark futures contracts were ahead 6 cents at $3.42 a pound in morning action on the Comex division of the New York Mercantile Exchange.

The

PowerShares DB Base Metals

(DBB) - Get Report

exchange-traded fund, which tracks futures prices of aluminum and zinc as well as copper, was ahead by 1%.

"Not only are we entering the bullish post-summer period, but ... stocks are still critically low," writes William Adams, an analyst at

BaseMetals.com

in London, in a daily market brief.

Other market observers noted trading volumes were light as many traders had taken time off to celebrate the Jewish New Year.

Elsewhere in base metals, steelmaker

Nucor

(NUE) - Get Report

said it would likely not meet consensus earnings expectations for the quarter ending in September. Still, the shares were rallying almost 4% after the firm said it would buy

Nelson Steel

for $54 million.

Turning to precious metals, gold prices were sliding again on more profit-taking, with December-dated contracts slipping $6.80 to $713.90 an ounce in recent action, while silver prices were down also, off 20 cents at $12.50 an ounce.

The bullion ETFs, which hold inventories of the metals, were also losing ground. The

streetTracks Gold Shares

(GLD) - Get Report

and

iShares Silver Trust

(SLV) - Get Report

were off 0.8% and 1.2%, respectively.

In other commodities, wheat prices were edging up 2 cents to $8.62 a bushel, buoyed by news of strong buying from Japan.

Corn prices were down by 2 cents at $3.55 a bushel, hurt by falling exports of the grain.

Cocoa prices were slipping $22 to $1,807 a ton on news that production of the beans would jump 10% in the 2007-2008 season.