Copper drifted lower yesterday as investors looked past a weaker US dollar, worried that scant demand outside China would stall a run-up that has more than doubled the metal's price this year.

The greenback's slump to one-year lows against the euro, which makes commodities cheaper for holders of other currencies, helped copper post modest gains earlier in the session, before demand concerns weighed on sentiment.

"We are seeing early signs of demand picking up in the world outside China, but I won't say that there is conclusive evidence that this is happening at a pace that is significant," said Yingxi Yu, analyst at Barclays Capital.