After six weeks of trading within a narrow range, the September and December contracts exploded to the upside on Tuesday, mostly on buying by commission houses, according to John Tyree, a broker at Fimat in New York. Gains were extended by the tripping of buy stops, or preplaced purchase orders.Some participants regarded the follow-through buying Wednesday as slightly disappointing, as the market met stiff resistance from selling by producers on the day's highs. But the market eked out another higher close based on speculators' returning to do more buying at the close of the session, said Ron Mark, a broker and analyst at Price Futures Group in Chicago.

Stocks in London Metal Exchange-registered warehouses have been declining steadily since April, down to 449,325 metric tons Wednesday from more than 800,000 metric tons four months ago. That is seen as evidence of a tighter market."The stocks have been the major driving force in London for this rally," said one New York-based trader for a trading house based in London.

"It's the tail end of the summer doldrums, the September-December rollover is all but over and now the market's free to move and get in line with the current stock situation."Traders roll over positions from one month's futures to the next active month when the first month's futures get close to expiration.

"I expect general consumer activity throughout the fourth quarter to sustain this rally and maybe even move [prices] higher," the trader said.Although he expected some resistance to gains in LME copper, the trader said he was confident the Comex market was no more than "a week away from sustaining 90 cents.

"The release Tuesday of new-home sales figures by the U.S. Commerce Department was viewed as a supportive factor, showing a 14.7% increase in July over June, the largest increase since April 1993. Copper wiring in new houses is a major source of demand for the metal.

The rally also likely benefited from a monthly report by research group Bloomsbury Minerals Economics Ltd. on Tuesday that projected a 329,000-ton supply deficit in refined copper for 2000. The report underlined the fact that consumption, running 6.2% higher than last year, was outpacing output, up 2.4% on 1999.

"This is something we were expecting," said Dave Meger, senior metals analyst at Alaron Trading in Chicago, who has been talking of the market's formidable fundamental supply-and-demand strengths all through what should have been a slow summer.

In other commodity markets:
COCOA: Futures gained on the Coffee, Sugar & Cocoa Exchange because of buying by local traders and short covering, or the buying of futures to balance previous sales, participants said. The December contract added $16 to $801 a metric ton. Buying also triggered buy stops, observers said.

-- Dow Jones Newswires