Copper prices sunk to their lowest in almost 20 months as persistent worries that a recession would dampen metals demand hit a market with thin summer volumes.

"That dollar strength yesterday was the trigger that came on top of the recent recession fears, pulling the rug from under the market," said Ole Hansen, head of commodity strategy at Saxo Bank in Copenhagen.

"The weakness overnight looks like it was driven by China and the COVID problems they're still facing. And this is the time of year where the market can easily get caught on the wrong side when liquidity is drying up."