Vale SA workers are set to extend a strike at a nickel mine in Canada after a five-month walkout that took about 10% of world supplies off the market and pushed up prices. Vale and United Steelworkers’ Union negotiators are at an impasse on issues that prompted workers to walk off the job in July, with no talks planned. About 3300 of almost 4600 employees at Sudbury halted work on 13 July after talks broke down over a labor contract, paralyzing output and leading to the longest strike in Vale’s 67 year history. Workers joined the strike in August at its Voisey’s Bay mine, Labrador. The strike tightened nickel supplies and boosted premiums paid for the metal in the US Midwest by 25%. Nickel output at Sudbury, Vale’s biggest nickel mine, slumped 74% in the third quarter from a year earlier to 5000 metric tons, while Voisey’s Bay output shrank 88% to 3000tns, Vale said in its third-quarter production report.