Copper rose almost 3 percent on Wednesday after China raised value-added tax on a range of metal ore imports, but metals across the board still look set for their worst annual falls on record.

China said it would raise value-added tax to 17 percent from 13 percent on a wide range of imported ores and concentrates from Jan. 1, a move analysts said aims to stablise domestic metal prices. But traders and analysts warned that new lows could loom next year even as base metals head for unprecedented losses this year.

"The VAT issue is helpful but there are bigger issues that will come to the fore such as the magnitude of the demand slowdown within China," said Nick Moore, commodity strategist at RBS Global Banking & Markets.