Shanghai copper prices slid for the first time in eight days on Tuesday, while London copper continued to lose ground as the dollar strengthened and BHP responded to a proposal from unionised workers at its Escondida copper mine in Chile.
The most-traded August copper contract on the Shanghai Futures Exchange fell as much as 1 percent to 53,730 yuan ($8,391.51) a tonne, and was trading down 0.6 percent at the mid-session interval.
In a statement on Monday, BHP said it was ready to discuss the "different points of interest" and hoped for a "mutually beneficial agreement" after the copper mine's union called for a salary increase of 5 percent and a one-time bonus of $34,000.
Copper investors "remain cautious, with the continued closure of Vedanta's Tuticorin smelter in India as well as the potential for strike action at Escondida," ANZ wrote in a note.
A unit of Chinese state-run conglomerate CITIC Ltd will buy a near 20 percent stake in Canada's Ivanhoe Mines for about C$723 million ($555 million), the companies said on Monday.
The Canadian province of Quebec will offer C$100 million ($77 million) in loans and guarantees on loans to steel and aluminium companies hit by recent US tariffs, the province's economy minister said on Monday.
Brazil's Vale on Monday unveiled a $690 million financing to expand a Canadian nickel mine, agreeing to sell unmined cobalt from Voisey's Bay as a booming electric vehicle market propels demand for the critical battery ingredient.