London copper jumps

Melbourne
Copper jumped on Wednesday as short sellers rushed to cover their positions amid speculation about further stimulus from China, and ahead of a policy decision from the U.S. Federal Reserve.
Asian shares clung to modest gains on Wednesday on pledges Beijing would buy more shares if needed, while caution ruled elsewhere before the Fed ends a two-day policy meeting later on Wednesday with markets divided on whether it will take a hawkish or dovish stance.
Three-month London Metal Exchange copper gained 0.28 percent to $5,312.50 a tonne by 0742 GMT, climbing $12.50 above the previous session's close.
Shanghai Futures Exchange copper surged 2.49 percent to 39,090 yuan ($6,297) a tonne.
Traders said the rally was sparked by short-covering. "The market always going to be prone to a short-covering rally, but it will most likely fail all things being equal ... what has (fundamentally) changed?" said a broker in Hong Kong.