Sept. 19 (Bloomberg) –Freeport-McMoRan Copper & Gold Inc. (FCX)'s Peruvian copper miners may strike on Sept. 27, a union official said, as they returned to their jobs this weekend after a four-day work stoppage.

Workers at Freeport's Sociedad Minera Cerro Verde SAA (CVERDEC1) mine ended the strike Sept. 17 after it was declared illegal by the government and clashes with police left six workers wounded, union General Secretary Leoncio Amudio said. Government-brokered talks aimed at a one-year accord are scheduled to resume again today, Amudio said.

"The company has acted in bad faith," Amudio said yesterday in a phone interview from the city of Arequipa, 750 kilometers (466 miles) southeast of Lima. "Conciliation has failed so far, and after this brutality, there's no way we'll accept a long-term agreement."

Workers in Peru, Chile, Bolivia and Indonesia have walked off their jobs at copper, gold and zinc mines this year, seeking better working conditions and a larger percentage of record profits. Miners at Cerro Verde held a 48-hour strike earlier this month and Freeport's Grasberg copper and gold mine in Indonesia began a month-long strike Sept. 15.

Freeport doesn't expect an immediate impact on copper output from the Cerro Verde strike, the unit's general manager Bruce Clemens said Sept. 15. The company will keep seeking a labor accord with the union, Clemens told reporters at a conference in Arequipa.

'Workers Cheated'
Cerro Verde, which is studying a $3.5 billion expansion to increase annual copper output by 45 percent, produced 312,336 metric tons last year. Grasberg produced 553,000 tons in 2010.

Freeport, not the government, must solve its labor issues, Peru's Energy & Mines Minister Carlos Herrera said Sept. 16.

Freeport risks having strikes drag on by not engaging more actively in negotiations, said Juan Muniz, a mining consultant and former operations manager at Cerro Verde. The company has sent a lawyer with a written proposal to the government- brokered talks, the union says.

"The workers feel like they're being cheated out of money that was already promised," Muniz said in a Sept. 16 interview. "Cerro Verde should take a more hands-on, human approach and actually sit down and negotiate."

Freeport spokesman Eric Kinneberg didn't immediately reply to an e-mail seeking comment outside office hours.