Copper also settled lower on news that BHP Billiton had sat down to negotiate an end to a labour strike affecting Escondida, the world's largest copper mine in Chile. COMEX copper for September fell 4 percent, or $14.80, to end at $3.4765 a lb.
London Metal Exchange's three-months copper fell 4.8 percent before recovering a little to close 3.9 percent down at $7,875 a tonne.