* FY copper output seen at 635,000 T from 665,000 T
* Maintains FY cash cost expectations at $1.47 per pound
* Shares fall more than 2 percent (Adds more details, shares, analysts comment)
By Olivia Kumwenda-Mtambo
Oct 28 (Reuters) - Chile's Antofagasta Plc on Wednesday cut its annual copper production forecast for the third time this year, sending its shares lower as the miner posted steady output in the third quarter versus the second.
Antofagasta shares, down 29 percent this year, fell 2.3 percent to 532 pence as of 0934 GMT.
Like its peers, London-listed Antofagasta is battling a slide in commodity prices as a result of slowing growth in China, the world's top consumer of industrial metals.
The miner has this year also been hurt by declining ore grades, unfavourable weather and environmental protests.
It cut its full-year copper output guidance to 635,000 tonnes from 665,000 after delayed ramp-up at its Centinela Concentrates operations and a minor pit wall slide at its Centinela Cathodes operations.
The company had to suspend operations at its Centinela, Michilla and Antucoya operations in March due to unusually heavy rains in the Atacama desert.
Antofagasta said its copper production in the third quarter was 157,000 tonnes, in line with the second quarter.
The miner had been focusing on its $1.9 billion Antucoya greenfield project and other brownfield expansions to cope with a fall in production, due to ageing mines and declining copper grades.
It said on Wednesday that it achieved its first output at Antucoya in September, producing 2,200 tonnes of copper cathode.
Net cash costs were down 11.3 percent quarter on quarter to $1.42 per pound and the company maintained its net cash cost guidance for the year at $1.47 per pound.
"That cash cost guidance remains intact is a bonus provided by the macro environment, however still not ideal in a falling commodity price environment," Investec analysts said in a note.
"We remain bearish on the stock and warn investors of increasingly reduced dividend potential from weaker earnings profile, high capex spend and acquisition of Zaldivar undermining the balance sheet."
Antofagasta agreed in July to buy a 50 percent stake in Barrick Gold's Zaldivar copper mine in Chile for $1 billion in cash..
The deal is expected to close in the fourth-quarter of this year, the company said.
The company is targeting savings of about $160 million this year and its chief executive told Reuters earlier this month it had cut back on exploration to cut costs.
Antofagasta Minerals, the group's operational division, said earlier this month it was reducing its workforce by around 7 percent. (Reporting by Olivia Kumwenda-Mtambo; Editing by Jason Neely and Mark Potter)