Activist investor Carl Icahn, the third-largest shareholder in Freeport McMoran Inc. (NYSE: FCX), said on Sept. 13 he endorsed the U.S. miner's efforts to reduce debt and explore strategic alternatives.

Icahn's comments come a day after Freeport said it would sell its deepwater Gulf of Mexico oil and natural gas assets to Anadarko Petroleum Corp. (NYSE: APC) for $2 billion in a bid to reduce its debt.

The billionaire investor, who owns a 7.8% stake in Freeport and has two representatives on the board, said last year the company was undervalued and needed to address several corporate governance and capital issues.

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"Yesterday's announcement demonstrates the company is making good on its stated goal of deleveraging and is on track to cut its net debt by half, from year end 2015 through the end of next year, at current copper prices," Icahn said in a statement on Sept. 13.

Freeport, like other miners, has been hit hard in recent years by a downturn in prices for commodities, including copper, gold and oil, even as it racked up debt due to acquisitions.

The sale to Anadarko follows failed attempts by Freeport to sell all or part of its oil and gas business. In May, Freeport withdrew plans to launch an IPO for the business.

CEO Richard Adkerson said in July that Freeport was still open to considering "all strategic moves" including selling assets or the entire company.

However, the company had then put its asset sales plan on the rear burner, and instead unveiled a $1.5 billion share issue to help cut debt.

Anderson also said he was confident the company could reduce its $18.8 billion of net debt to between $13.2 billion and $10.5 billion by the end of 2017.

The company's share price has more than doubled since it touched a 16-year low in January.