The slip has hurt miners bottom lines in recent months.
Rising stockpiles of metal at exchanges have added to worries, compounding the impact of souring sentiment in broader markets.
“The trend in copper is now clearly down, with crude oil prices perhaps the next in line to resume a downward trend. Funds are likely to remain cautious until the 17 April meeting of key oil producers,” said analysts at ANZ in a note to clients.
Three-month copper on the London Metal Exchange (LME) closed unchanged at $4,650 a tonne on Friday, still near a six-week low hit in the previous session, when it slumped 2.8 per cent in the biggest daily loss since September.
Copper shipments into Singapore jumped 4,800 tonnes in March, LME data has shown, fuelling concerns China will ramp up exports to global markets due to domestic oversupply.
Zinc also fell sharply last week, losing six per cent on the LME.