Russia on Wednesday said "certain progress" had been reached at expert-level talks on Iran's nuclear programme despite the Islamic Republic's tough terms for scaling back its enrichment activities.
Tuesday's meeting in Istanbul was held after a fourth round of talks between top negotiators on the escalating crisis held in Moscow last month ended in stalemate.
The experts agreed in Istanbul to go ahead with a more senior meeting between EU and Iranian diplomats at a future but still unspecified date.
Russia's Deputy Foreign Minister Sergei Ryabkov said Moscow was satisfied with the outcome despite the broad disagreements that remained.
"I cannot say that we reached some sort of breakthrough or achieved decisive progress," Russia's chief negotiator on the standoff told Interfax.
Signup to our newsletter and follow us on Facebook and Twitter!
"But we are not losing heart or think that the Istanbul meeting of experts was a failure," Ryabkov added.
"On the contrary, there are grounds to speak of certain progress."
A statement from EU foreign policy chief Catherine Ashton -- head negotiator for the five permanent UN Security Council members and Germany who make up the so-called P5+1 group -- said simply that talks focused on "technical subjects".
It said the two sides continued to discuss the world powers' earlier call for Iran to immediately stop enriching uranium to the high level of 20 percent in exchange for some forms of economic assistance.
Iran has instead sought recognition of its formal right to enrich uranium -- something that contradict current UN resolutions -- and sought an end to oil sanctions that have seen its vital exports nearly halve so far this year.
Ryabkov said Moscow was willing to support its close trade and military partner's right to enrich uranium as long as the Islamic Republic subjected its nuclear programme to strict international controls.
"The right to enrich and recognition of this right must come in exchange for the Iranian unclear programme coming under comprehensive international control," Ryabkov said.