The Russian envoy to the Iran nuclear talks in Vienna said on Tuesday that the working group was making "indisputable progress."
"Sanctions lifting is being actively discussed in informal settings," added envoy Mikhail Ulyanov on Twitter.
Ulyanov is attending the 8th round of the Vienna Talks, which are about reviving the Joint Comprehensive Plan of Action (JCPOA) by bringing the United States back into the deal through sanctions lifting, and Iran through full implementation of its nuclear commitments.