International Energy Agency executive director Claude Mandil said Monday that current oil prices aren't sustainable. "The current prices aren't sustainable," Mandil told a media briefing. "The high oil prices are not consistent with the long term trend just because they are much higher than the margin costs of an additional barrel," he said, with each barrel costing about US$25 to USS$35 to produce. Oil prices are now hovering around US$70 a barrel. "Even producers aren't happy with the high prices," Mandil said, citing concern about potentially weakening demand.