Kennecott said it couldn't offer any details beyond Thursday's statement.

"While still in the early stages of recovering from the impacts of the slide, Kennecott is looking ahead at plans for how to adapt to a 50 percent decrease in production this year," the company said.

"While we still don't have all of the answers, we have reached a point where additional measures are necessary to reduce operating costs. Additional changes to reduce our operating costs may be required as operating plans are finalized in the coming months," it said.

A week ago, Kennecott opened the mining pit to view for the first time since the landslide, which geologists say moved enough material to nearly fill up the Panama Canal.

Rock and dirt without ore value washed over the terraced steps of the mining pit that's nearly a mile deep. The slide left the tip of one giant electric-powered shovel poking out of the dirt and a collection of mangled haul trucks. Kennecott has said the slide buried three shovels and 14 trucks, many out of view.

It will take months for the major U.S. copper mine to recover, even though Kennecott has said it anticipated the landslide. It ran farther than expected, unleashing what the U.S. Geological Survey has calculated as 128 million cubic yards of rock and dirt. That's two-thirds of the material removed for the Panama Canal.

Market analysts said the worst-case scenario has Kennecott losing sales of up to 165 million tons of refined copper in 2013.

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