GENEVA- A round of Syria peace talks that ended on Thursday was a big missed opportunity but there may more talks next month if ideas can be found to encourage President Bashar al-Assad's government to engage, UN mediator Staffan de Mistura said.He said neither side had actually "sabotaged" the latest talks by refusing to attend but he laid most of the blame for the failure of the round at the feet of the government side.De Mistura voiced milder disappointment with the Syrian opposition, after they arrived in Geneva ruling out any future role for Assad. But he said that tough public stance had been tempered by a mature position in the closed-door discussions."The goal we had was to bring about real negotiations," de Mistura told a news conference. "Let me be frank. We did not achieve, we did not achieve these negotiations. In other words, negotiations in reality did not take place."I would conclude by saying (it was) a big missed opportunity. A golden opportunity at the end of this year when in fact there is a clear indication by many sides that the military operations are coming to a close," he added.