SANTIAGO, Sep 23, 2011 (Dow Jones) -- International copper prices, which have taken a pummeling this week, may have touched rock bottom, the chief executive of Chilean state copper company Corporacion Nacional del Cobre said Friday.

"You get the feeling it's hitting bottom...the supply and demand equation still remains tight," said Chief Executive Diego Hernandez.

On the back of intensifying fears about sluggish U.S. growth and Europe's ongoing debt troubles, three-month copper on the London Metal Exchange dropped 7.3% to $7,115.75 a metric ton, its lowest level in 13 months, before paring back some of its losses on Friday. Copper ended 4.1% lower on the day at $7,355 a ton.

"We're optimistic about copper in the medium-to-long term," even if copper prices see a lot of volatility over the short term, he added.

Codelco, as the state-owned miner is called, is the world's biggest copper mining company. With an annual output of around 1.7 million metric tons of copper, Codelco produces 11% of the world's copper.

Chile produces a third of the world's copper supply.