London Metal Exchange (LME) copper closed floor trading above $3,400 a tonne on Wednesday and within sight of last month's record high of $3,435 in a market dominated by tight supply, dealers said. Three months copper ended at $3,404, up $9 from Tuesday's kerb close but off a high of $3,414 on the day.
"A close above $3,400 could be the launchpad to hit a new record the bulls are after," a dealer said.
"That said, repeated producer selling and profit-taking when prices move above $3,410 is causing a bit of uncertainty, although the right fundamentals remain in place for a rally."
LME stocks remain around 31-year lows despite a rise on Wednesday, while other supply worries persist.
BHP Billiton Ltd/Plc. said it had halted mining at its Olympic Dam copper and uranium mine after a fatality there.
Striking workers at Zambia's Nchanga copper mine rioted in violent protest over wages.
And US copper miner Asarco, which has slashed output for the past two weeks as a result of a labour strike, will meet union leaders on Friday.
"Copper's action on the charts looks impressive as since July 1 buying has entered at ever higher levels, which could force a re-challenge of recent highs at $3,411 and $3,435," Basemetals.com's William Adams said in a daily report.
Average prices for most LME traded metals are seen in sharp decline in 2006 as supply bottlenecks ease and demand falls, but they will stay at historically high levels, a Reuters poll shows.
Mining stocks, including Rio Tinto, advanced on the FTSE 100 index after data showed unexpected strength in China's economy in the second quarter of this year reflecting a stoke in demand for raw materials.
Rio Tinto was among the top gainers, rising 3.4 percent as it reported record quarterly Australian iron ore production, while BHP Billiton climbed 3.5 percent and Antofagasta gained 2.7 percent.
World lead and zinc prices were boosted after a labour strike at Teck Cominco's plant in British Columbia, Canada amid reports it had declared force majeure on sales, while deliveries from stocks continue until depleted.
Aluminium ended at $1,832, up $9, while zinc was at $1,240, up $30.
Tin and nickel were also up, although lead closed down $1 at $841.