Workers at Chile's Altonorte smelter are close to reaching a wage deal with owner Xstrata to end a near week-long stoppage, union leaders said on Sunday.

The strike, coupled with a looming disruption at state-owned Codelco's Chuquicamata copper complex, the world's second largest, helped lift global prices for the red metal, fanning supply interruption fears in the world's No. 1 producer, Chile.

The Altonorte complex produced 232,000 tonnes of copper anodes last year. Global miner Xstrata said the stoppage coincided with general maintenance at the plant, which lowered anode output to a minimum. Maintenance work, which is carried out every 2-1/2 years, is due to end on Jan. 20.

We are close to signing a deal to end the strike, said Abdiel Sepulveda, head of Altonorte's union No. 1. There are still a few details pending to formalize the signing tomorrow, he added, but said a deal was still not yet certain.

If the deal is signed on Monday, workers could resume operations later the same day, Sepulveda said.

The 274 union workers, which represent about 90 percent of the labor force in charge of production, downed tools on Monday.

Analysts have said a prolonged strike at the Altonorte smelter could delay some anode shipments and force mining companies to sell concentrate to other smelters.