Three-month copper on the London Metal Exchange (LME) CMCU3 fell 1% to $8,940 a tonne, after rising 2.9% in the previous three sessions.

U.S. Comex copper futures HGc2 fell 0.7% to $4.04/lb.

LME copper has fallen 19% since hitting a record peak of more than $11,100 a tonne in May. However, copper has narrowed its losses after workers at BHP's BHP.AX Escondida mine in Chile went on strike, paving the way for production at the world's largest copper mine to be affected.

LME inventories surged on Tuesday to their highest level in nearly five years, more than doubling in the past two months.

“For copper, this is a pretty negative signal. It makes people a little nervous that there might be a bigger surplus than we realize,” said Dan Smith, director of research at Amalgamated Metals Trading.

Traders said recent flows into Asian LME warehouses suggest China is exporting excess material.

The latest data also raised concerns, showing Chinese bank lending fell more than expected in July to its lowest level in nearly 15 years, highlighting weak demand in the world's second-largest economy.

Some actual consumers in China, including from the state grid, have been buying to take advantage of recent weak prices, which has helped to cushion the blow, according to a copper producer in China.

Market positioning was also a factor, with some speculators selling to take short-term profits from the recent rally, a trader said.

"We're trying to figure out where the bottom is for copper. I feel like we could see a little bit of a pullback. These pullbacks tend to be long-lasting and copper at $9,000 isn't exactly cheap," Smith said.

LME zinc and lead fell after more new LME stocks arrived, with zinc CMZN3 slipping 2.2% to $2,683 a tonne and lead CMPB3 down 2.7% to $1,992.50.

Among other metals, aluminium CMAL3 LME rose 0.9% to $2,325 a tonne, nickel CMNI3 fell 0.1% to $16,335 and tin CMSN3 fell 0.9% to $31,280.