Copper has climbed, boosted by a lower greenback after the US central bank left rates unchanged and some expectations of steady demand in top consumer China.

London Metal Exchange benchmark copper ended up one per cent at $US4,896.5 a tonne. The metal used widely in power and construction touched a two-week low of $US4,830 a tonne on Wednesday.

The Fed said near-term risks to the economic outlook had diminished, but gave no firm indication of whether it would raise rates at its meeting in September.

Demand for copper in China, which accounts for nearly 50 per cent of global consumption estimated at around 22 million tonnes this year, has fallen sharply in recent years as growth and investment spending has slowed.