0205 GMT - Delivering new, large-scale copper supply will likely be more costly, slower and riskier than anticipated, says Jefferies. That justifies higher copper prices and reinforces the case for miners to buy copper growth, rather than building new mines, in some instances, it says. In a review of major projects, the bank found many failed to deliver the production volumes expected when a final investment decision was made. A "combination of capex inflation and production underperformance suggests that industry forecasts may systematically overestimate the amount of copper supply likely to be delivered from greenfield projects and underestimate the true incentive price to build new mines," Jefferies says. "The implications for copper supply are significant" and support premiums increasingly being assigned to some operating mines, brownfield expansions and "derisked" development assets, it says.