Copper sunk to a five-month low overnight as a firmer US dollar and anxiety about the fallout on growth and demand from the US-China trade dispute outweighed dovish comments from the US Federal Reserve chairman.

Benchmark copper on the London Metal Exchange fell 1.5 per cent to $US5,792 a tonne in after-hours electronic trading – the weakest since January 4.

It had shed 0.6 per cent to $US5,807 a tonne in closing open outcry trading, reversing direction after earlier touching a high above $US5,900.

The market has been losing ground in recent months on worries about demand in China, which accounts for around half of global consumption of industrial metals.

“It still all comes down to trade and without a resolution there, things haven’t really changed even if the Fed does cut,” a copper trader said.

Metals got a fillip in the morning after the Fed chairman said on Tuesday the central bank will respond “as appropriate” to the risks posed by a global trade war and other recent developments, remarks that seemed to open the door to the possibility of a rate cut.

The US central bank meets June 18-19.

“The Fed can blunt the impact of a slowdown from trade taxes. It probably cannot stop a slowdown from trade taxes,” UBS analysts said in a note.

The US dollar index was slightly firmer by the LME close, having recovered after earlier falling to an eight-week low.

A stronger US currency makes US-dollar-denominated commodities more expensive for holder of other currencies, which could potentially crimp demand.

This is a relationship used by funds to generate buy and sell signals from numerical models.

Metals markets are looking ahead to industrial production and investment data from China for clues to demand prospects over coming months.

Also on the radar is a meeting of the Group of 20 countries in Japan over the weekend, where trade tensions will be a major topic of discussion.

Nickel, untraded in closing rings, was down 0.8 per cent at $US11,720 a tonne in electronic activity, the lowest since January 24.

It slipped on worries about weaker demand from the stainless steel sector, which accounts for two-thirds of global demand estimated at about 2.4 million tonnes.

Also weighing on nickel are increases in stocks in LME-approved warehouses, which have been on a downtrend since late 2017.

Latest data shows stocks are up 5,136 tonnes at 164,052.

Aluminium finished 0.8 per cent weaker at $US1,771 a tonne, zinc ceded 0.6 per cent to end at $US2,461.50, lead added one per cent to $US1,865 and tin rose 0.4 per cent to $US19,175.