(Adds comments from statistics agency, data on copper output)
SANTIAGO, March 30 (Reuters) - World No. 1 copper producer Chile produced 447,810 tonnes of copper in February , a 1.1 percent decrease from a year earlier, due to plant maintenance at a key project, the government said on Monday.
Chile, which produces a third of the world's copper, is struggling with dwindling ore grades in many of its aging deposits, although new mines are helping to boost output.
"This result is explained by decreased extraction in the period due to programmed maintenance work at the processing plant of an important mine, which reduced production," the official INE statistics agency said.
The INE does not give details on the mines in question, but in February the massive Collahuasi copper mine temporarily halted its main grinding mill for minor maintenance work.
Collahuasi, one of the world's largest copper mines, is a partnership between Glencore Plc and Anglo American Plc .
In the first two months of the year, Chile produced 971,684 tonnes of copper, up 6.1 percent versus January to February 2014.
State copper commission Cochilco has forecast that Chile will produce 6 million tonnes of copper in 2015.
Production of molybdenum, a metal used to harden steel, fell 11 percent in February to 3,357 tonnes from a year earlier.
For the first two months of the year, molybdenum output was down 5.4 percent to 7,165 tonnes. (Reporting by Rosalba O'Brien and Anthony Esposito; Editing by Chizu Nomiyama and W Simon)