Freeport, the biggest U.S.-listed copper miner, said it is reviewing its mining and oil and gas businesses for significant additional cuts in capital spending and operating costs because of weak prices for copper, molybdenum, oil and gold.

Shares in Arizona-based Freeport leapt on the announcement, and were last up 9.4 percent at $12.44 on the New York Stock Exchange.

The stock has lost half its value this year on concerns about Freeport's heavy debt load and a slide in copper prices to six-year lows. Copper was last bid at $5,305 a tonne, or $2.41 a pound.

Freeport may reduce production at some of its North American operations as it did in 2008-2009 to cut costs, Morningstar analyst Daniel Rohr said.

"There are some smaller mines that would probably struggle at, say, $2.30 copper," he said.

Molybdenum is produced as a by-product at some of the copper mines.

Freeport does not give data for costs at individual mines. The net cash cost for producing a pound of copper was $1.74 at its suite of North American mines in the three months to the end of June. The net cash cost for a pound of copper was 81 cents at the company's Indonesian operations, $1.07 at its Tenke mine in Africa and $1.90 in its South American operations.

Freeport aims to complete this review "promptly" and report back on its plans in the third quarter. Company spokesman Eric Kinneberg declined to comment further.

Output cuts are going to be the "general theme in most commodity markets over the next year," said Ed Meir, metals analyst at INTL FCStone.

Although the cost and spending reductions are a step in the right direction, investors are likely to continue to focus on Freeport's heavy $20.9 billion debt load, Jefferies analyst Christopher LaFemina said in a note to clients.

LaFemina said the real solution for Freeport would be to issue equity. He noted that the window of opportunity for a previously announced initial offering of a minority stake in its oil and gas business may have closed.

"A dilutive equity issuance would probably be a positive for the Freeport stock price as it would shift the market's focus back from balance sheet to P&L (profit and loss) statement," he said.

(Reporting by Nicole Mordant in Vancouver; Additional reporting by Josephine Mason and Luc Cohen in New York; Editing by Paul Simao)

By Nicole Mordant