Iran's top nuclear negotiator Saeed Jalili on Friday expressed optimism that weekend talks attended for the first time by the United States over their nuclear standoff would be constructive, provided Washington came with the right approach. "What is important for us is with what approach they come to the talks. If it is with a constructive approach, and that they refrain from past mistakes, then for sure we will have constructive talks," he was quoted as saying by the official news agency before leaving Tehran for Geneva.