"Workers at Southern Peru Copper Corp's two mines, Toquepala and Cuajone with combined concentrate capacity of around 350,000 tonnes a year, are asking for a wage increase and a revision of the current contract, and plan to go on strike on 31 August.
This development is price supportive," said Barclays analyst Ingrid Sternby. A SPCC official said the company had begun negotiations and planned to do "everything possible to avoid a strike."
He said three of the nine unionised sections at the Toquepala and Cuajone mines were involved in the dispute, but could not say how many workers. He said the Ilo operations in Southern Peru were not affected.
Analysts said miners were seeking higher wages amid firm copper prices, and jitters over a strike during an overall bull market helped it extend gains from Wednesday's one-month low, though stiff resistance limited its ascent.
COMEX December rose 1.00 cent to $1.2505 a lb on the New York Mercantile Exchange, after trading from $1.2350 to $1.26.
Resistance lurked at the $1.25-$1.26 area, with support at $1.2165, brokers said. In other months, September was up 1.10 cents to $1.2505, spot August gained 0.95 to $1.2515, with the rest 0.85 to 1.00 higher.