Changes in the outlook for copper's supply-demand balances that drove a recent rally in prices support a more "bullish" environment for the metal at least to mid-2017, Goldman Sachs said in note.

"Although it is tempting to blame this on speculative positioning, the materially stronger fundamental developments that contributed to this surge in speculative interest are likely to underpin a more bullish environment for copper," Goldman analysts wrote in a note dated on Sunday.