* Cerro Verde is country's third-biggest copper mine
* Workers say could launch indefinite strike on Sept. 14
* Company says "no material impact" seen on production (Adds details on company measures)
By Caroline Stauffer and Teresa Cespedes
LIMA, Sept 7 Workers at Cerro Verde in Peru launched a two-day pay strike on Wednesday but no impact on output was expected at the mine that produces around 2 percent of the world's copper, union and company representatives said.
The 1,100 workers started the strike after last-minute talks with the company broke down on Tuesday and they threatened to lay down their tools indefinitely on Sept. 14 if their demands for higher wages are not met.
But Freeport McMoRan (FCX.N), which has a controlling stake in the mine, said it expected output to remain unaffected.
"Cerro Verde does not anticipate that the strike will have a material impact on production," spokesman Eric Kinneberg said. "We will continue negotiating a new labor contract to replace the one that expired on August 31, 2011."
Kinneberg did not provide details, but the Cerro Verde union's leader told Reuters the company had copper stockpiled and had temporarily contracted outside workers.
"Usually they have stocks that can support five to eight days without affecting output," said the union's secretary-general, Leoncio Amudio. "They have also hired people for three months, about 400 workers."
Supply worries caused by the strike, combined with a planned walk-out on Sept. 15 at Freeport's mine in Indonesia, helped push copper prices CMCU3 up to $9,092 per tonne versus $8,933 a tonne from Tuesday's close. [ID:nL5E7K71CT]
Workers at mines throughout the developing world have gone on strike in recent months, demanding a greater share of mining profits at a time of record-high metal prices.
Shougang Hierro Peru (SHP.LM), Peru's only iron producer, declared force majeure on its deliveries last week due to an ongoing strike.
Cerro Verde (CVE.LM) produced 312,336 tonnes of copper in 2010. Peru is the world's No. 2 producer of copper and silver and the No. 6 gold producer. Minerals account for 60 percent of its exports. (Additional reporting by Patricia Velez; Editing by Dale Hudson)