London Metal Exchange (LME) copper sprang higher in kerb trading on Tuesday, with bank and trade buying propelling the price above the 10-day moving average, which triggered further buy-stops, dealers said.
Copper moved back into positive territory in kerb trading and now had $2,800 a tonne in sight, although the move left traders puzzled given the absence of fundamental news.
"The price passed the 10-day moving average at $2,739 a tonne on what seemed to be bank and speculative buying interest," a trader said.
"Above that it triggered some buy-stops and that appeared to have encouraged further interest."
Other traders said persistent bank buying interest had encouraged similar moves by the trade and now resistance at $2,800 was targeted.
Copper closed the kerb at $2,754 a tonne, up $31 from Monday's kerb close.
Ingrid Sternby, analyst at Barclays Capital, said copper's outlook remained upbeat and expected demand to pick up after the mid-year slowdown.
Peru's Labour Minister Javier Neves brokered fresh talks on Tuesday between Southern Peru Copper Corp and union leaders to try to end a strike for higher wages now in its eighth day, officials said.
"The strike is still on but we're hoping it will end today with a deal with the company in negotiations with the help of the labour minister," Ruben Arenas, a senior union leader at Southern Peru's Toquepala pit, told Reuters.
Strong gains in copper washed through to other markets.
Aluminium rose to $1,676, up $15 on trade buying, while nickel jumped $150 to $12,375.
Tin bounced up as consumers took advantage of earlier six-week lows at $8,550. The price ended at $8,850/875, gaining $140.
Lead closed $15 higher at $868, while zinc edged up $12 to $974.